Is Google Tag Manager Preview Mode Not Working? 22 Ways To Fix It.

yes yes, everything else is ok. I just started the preview mode again and same thing. Now only works when I refresh the page and then it pops up. Although normally it was open straight away when I opened the page.

But good that it works for most then haha :D

Hi,

Great list, would like to suggest one more. There was a new version of Chrome available and I just noticed it this morning. Updating and relaunching was the simple fix.

Thanks,

Jeremy

Turns out my problem was related to Cloudflare as this changed how the JS snippet was being pulled in. I changed to setting to optimise JavaScript and the preview mode started working.

Try logging in to GTM account and trying to replicate the issue in Chrome's Incognito mode. Maybe some browser extension is interfering.

What do you mean by saying "I do not find any of my accounts after I login"?

Triple check if you are looking at the preview mode of the same container.

Cheers. Turns out the idiot dev had installed the GTM code on all pages but the home page. As soon as I visited an internal page, the debug console loaded.

I had no idea gtag.js and gtm.js are different things. I was thinking that since I had gtag.js installed, it was Google Tag Manager as well. And for a whole day I was troubleshooting why debugging preview mode wasn't working until I understood that I had to install GTM myself... Maybe that helps someone else as well.

Will preview mode work on a site that requires log in?

Wow. This worked! Thanks so much. I was having a lot of trouble, but this solved it!!! Thanks again.

I had a case where the problem was in the GTM code, which was not written in the HTML file but in another js file called in the HEAD, was solved by removing the GTM code from the JS file and pasting in HTML file

Hello!

In the new version, not a single one of my gtm.clicks are showing up in the preview/debug mode. Is is also happenning to anyone else? And how can it be solved?

Thank you!

Hi Julius,

I got a new issue where it connected and then disconnected after a few seconds, not sure what is doing it...

Hi Julius,
I have tried 6 x other sites and they are fine, it seems to be just one. I have quite a few tags and triggers in the container. It is using latest GTM4WP plugin, and tried with and without debug url but still disconnects after a few seconds, i also have Adswerve turned off.

https://tagassistant.google.com/?cb=8055371684657917&waffles#!#source=TAG_MANAGER&id=GTM-WDT8L3T&gtm_auth=MEsI_nC-QTLmgVE0FWfT7Q&gtm_preview=env-6

#12 - If you are testing more than one page/URL, close all of the windows except Tag Manager and start over by clicking preview.

For me, I got the preview connected once, and then when I changed to check different pages/URLs, I kept getting a "Not connected" error on the website page and on the "Preview" page. Starting over resolved it.

I have another issue.
Don't know why, but now I have debugger popup with "No debugger found" on several pages - including this - and can't get rid of it (obviously, debugging is disabled and no domains listed in debugger).

Every time I go to a subdomain the debugger drops the connection. The GTM pixel is installed and works across both properties, but when I click on a link that takes me to the subdomain it drops.

I did get the debugger to stay open once using Gord Marwicks' suggestion.

In my case, I am dynamically loading the Gtm snippet, which was working fine with the previous preview mode in GTM. Now it shows "Tag Assistant could not connect to a tag on". I checked all the steps as mentioned by you, the only thing that works when i add gtm snippet manually in , but does not work when dynamically loaded.

Hi Julius,

First of all thanks for updating these and more articles regarding the new Preview & Debug version.

I was able to fix my time-out errors by applying solution #10.

But now I ran into the following problem;

The new Preview & Debug mode opens a new pop-up window, from which I can't change the fixed URL. Previously it was possible to navigate to a URL that cannot be reached through the website menu.

Is the above situation still possible with the new version?

Just tried removing tag assistant plugin from browser, its now working for me

The page will open in new window but you can see the timeout issue will be no more
©2020 Google

Allthough I see the new debug mode has a lot potential, at this moment it is also very frustrating. When a website is on a development domain and behind a firewall (I can only get access if my IP-address is on the whitelist) GTM doesn't work. Like other posts I get the message "connected" and within a few seconds Tag Assistant says "Not connected". Which is so frustrating as it is on a development environment for a reason and I need to get to test the tags before the website is finished and goes to production...

Just before the release of the new version I could test without any problems. So it seems the new GTM needs some kind of access.

(At another website the staging environment is secured with a login and then there is no problem). Unfortunately the choice for the method of security is not mine to make...

Thanks for this article.

In my case it was the "Avira Save Shopping" PlugIn in chrome browser which came with my Avira Antivirus installation. After removing this plugin everything worked fine.

Hi Julius,
Nice info all step have checked but still, my debug mode is not working if my site doesn't have an SSL certificate is this issue or not.
thanks

Hi so this is crazy what Google did. Nothing works.

Right now I am able click PREVIEW in GTM, and then Tag Assistant window shows connceted to Container. The web page also says debugger is connected. However, when I look at the tag assistant window, it says:

"GTM-XXXXX is not enabled for debug"

To start debugging this container:
Go to Tag Manager
Open container GTM-XXXXX
Click the Preview button
Start new debug session

Which is exactly the thing I did so I am in this endless loop of broken!! Any ideas why?

Hi, thanks for this detailed article, and for updating it for the new tool so quickly. Since this update we're no longer able to test though - it connects fine, but there are just no infos back in the debug window (variables, data layer, events etc) - nothing at all (except showing the different pages that have been navigated to, but not GTM info for that page). I've tried with and without the Chrome extension, but makes no difference.
Is this the link you're requesting in order to help out? https://tagassistant.google.com/#url=https%3A%2F%2Ffiit.tv%2F&source=TAG_MANAGER&id=GTM-KPFMTT7&gtm_auth=N31Puc189vSs87qTi4lu9g&gtm_preview=env-7

Thanks very much

I have a website which takes the customer information from x domain and populates the domin y with that information in the form. However if i give doain x url in the preview mode gtm gets disconnected as soon as it goes to domain y..the other thing i tried was using domain y url,, but in that case the form is empty since the information is lost when gtm reloads the page...any solution to the problem..

Every time I enter my domain for debugger mode, Google states it could not connect and the pop-up window shows a different website extension and previous a different website than mine. My website is https://www.xxxxx.com and it continuously changes it to https://www.xxxx.co.za and shows the wrong website in the preview. I have confirmed multiple times that I am entering it correctly and on the preliminary screens prior to the preview pop-up, the domain is correct. I have also tried to add a trailing slash and removing the debug signal in the URL. I am at a loss.

Hey guys, Im using a subdomain to qa and sometimes it shows connected but the windows in tag assistant never loads, this is the preview link: https://tagassistant.google.com/?waffles#source=TAG_MANAGER&id=GTM-5JRBXXZ&gtm_auth=gxXxHSZuE4p-lcyL-_sI6g&gtm_preview=env-3&url=https%3A%2F%2Fhomolog.sempreemcasa.dev

Hi Julius,

You are a hero for updating this article so fast after releasing the new debug design. I really like the update and I've worked with it for a couple days. However, since yesterday it suddenly stopped working.

I've tried all the above mentioned possible solutions, however, none of them works for me.

If I click preview in GTM I am redirected to tagassistant.google.com. There I type out the right website, and click "Start". The website opens and the bar goes halfway and stops there. Stays there for around 20 seconds and then says "Tag Assistant could not connect to a tag on http://eagledev.leadingcourses.com/en". However, in the tab with the new link opened I get the small screen in the right bottom saying that it is connected to the debugger with a specific emoji, and sometimes it says it could not find the debugger. However, in both cases the debugger on tagassistant.google.com is not working.

Some additional info: We are currently building a new website and I have Tag Manager installed on both the new and the old website. On the old website it works perfectly fine.

This is the URL to the debug session:
https://tagassistant.google.com/#url=http%3A%2F%2Feagledev.leadingcourses.com%2Fen

Hope you can help me!

My question is in addition to #15, our website has multiple environments like test, PreProd and production. Tip#15 is super helpful to debug the tags running on any of the environment. But I am still unable to preview my current changes in my workspace. In the previous version of GTM preview I was able to debug all the changes in workspace.

Hi Julius

The problem I'm having is that the GTM container sometimes loads and other times (at random) just doesn't. SO sometimes I see Message - DOM Ready - Window Loaded, but no container to fire the tags.
Any idea what could be happening here?
This is the preview URL: https://tagassistant.google.com/?cb=847854266750625#!#source=TAG_MANAGER&id=GTM-K3SLH5B&gtm_auth=HTCLZSisM80DdmjXCyEO2A&gtm_preview=env-6

I'm looking into solution #13. Where can I find the cookie named _TAG_ASSISTANT? I don't see it on several websites (including this one) if I check the cookies being set. How can I check if this cookie is being set or blocked?

Hi Julius,

I tried almost all of those above from the hints given, but none seems to work. I'm trying to debug an AMP website, and Tag Assistant keeps telling me that "a timeout occurred". I don't use any ads blocker whatsoever btw.

Any thoughts?

Sadly did not help.

Issue is, if I go a a browser and access the site all activity appears in the Real Time reports.

If I launch the site in preview mode, my active doesn't appear.

I did change 1 tag and added 2 variables.

Need to test the changes before going live.

Have asked client if it is OK for me to publish before I confirm tags are working correctly. If they say yes I'll try that and see what happens.

Not happy with the new GTM preview functions.

Tried everything, still no luck, and some quite weird behaviours:
1. Website: https://mateuszdabrowski.pl
2. When I click the Preview in tag manager and provide my website details, it opens the page and in the bottom right I see the pop up informing me that the Debugger is Connected.
3. When I go to the Preview Debugger it is stopping at about 60% load and timing out. The tab name is "Tab Assistant [Connected]" but in its header on the top left there is red "Not connected".
4. When I then go to the main page of tag assistant I see that my domain is active and have a button to "Stop debugging". But when I click it, it opens my website yet again and the debugger does the same as in step 2.
5. I have two tags in GTM - GA3 and GA4 (as per https://www.analyticsmania.com/post/upgrade-to-google-analytics-4/) and the tag is already published, as I did not want to lose the data. GA3 is working perfectly fine, showing real-time data and the standard one. GA4 is showing nothing. Despite being in the same tag published at the same time (previously I was using GA directly, without GTM, so for both solutions, it is the first time in a tag for this page).
Tried multiple browsers (Safari, Chrome, Firefox) was blocking content blockers and cross-site cookie tracking, nothing helps.

I read 3 google support forums and 2 other articles before stumbling upon this one --- crazy stressed I couldn't figure out why it said my tag wasn't on my site when it definitely was.

It was #5!!!! So simple and yet no one said to make sure it got done.

THANK YOU!!! Downloading your GTM guide ASAP!

Hi Julious,

My site is created by using SINGLE PAGE APPLICATION. With this new version of the preview mode, Page views are NOT captured when I navigate between pages. Hence, I see all events grouped in one single page container.

The developer that is helping me suggested to use 'History Change' as an alternative for 'Page View' as trigger. Now I can see the tags firing when I visit specific pages, but they are still grouped under the same Page container. This is not ideal.

Do you have any other idea to make Preview Mode work in this kind of sites?

URL here: https://tagassistant.google.com/#url=https%3A%2F%2Fwww.flip.co.nz%2F%3Fgtm_debug%3Dx

Thank you from Germany, didnt find such a complete article about GTM in german. Solved my problems. Thank you very much.

Here's a pesky one. Copied existing and functional page and pasted into a new file in Coda. Didn't realize I had the encoding incorrectly set. Page rendered fine, Google Tag Assistant sees it, no errors, but the debugger couldn't connect. Finally ran my page through https://validator.w3.org/ to figure out what the problem was.

Thanks! Had to go through all options to finally found out I had an extension called Disconnect which I forgot I had installed blocking it. Clicking "Unblock tracking" solved it. So if you're using this extension make sure it's allowing tracking on your website :)

Thanks for this article. Unfortunately, since this new version of GTM I can't succeed to make the preview work: "Tag Assistant could not connect to a tag on... A timeout occurred while attempting to connect." My GTM installation script is in the head, I tried with Google tag assistant or without any extensions activated in Chrome, I tried without and without "Include debug signal in the URL".. On Chrome, on Edge, on my different containers.. None work. I cannot find any solution to make this preview working.. An idea? Thanks

Hi Julius,

Thanks for these all guides. I love your articles.

My question is about GTM container.

I have a website and my website is copied by some people. All codes of my website is copied. So I can see visitor statistics of this copied version because my analytics code is also still in the code.

So I am thinking of using tag manager to intervene to copied version. I can create a HTML tag and add some style code that will make invisible all content like display:none.

I checked the GTM codes and yes, still my old GTM codes on the website. But GTM is not working. When I open the preview mode, debug mode works but find only gtag.js not GTM for this copied version.

Also GTM chrome extension find only gtag.js and analytics not GTM for copied version.

After my website is copied, the new page paths has index.html suffix. I dont know why there is index.html on the last of each page path. I guess this is related to copy system.

Can you help me? If I can make working GTM, I can intervene to copied version.

Possibly simplistic but it worked for me. Use Google Chrome as your browser, not Safari (for sure, possibly others). Hitting preview (in Safari) ran code but nothing happened, no window pop-ups etc. EVENTUALLY, I tried it in Chrome and it worked first time! Doh!

O`key guys! I found 1 way, spend on it solve 2 hours!
If you have Tag Assistant - do the connection to site, and when you see "Couldn't connect to.... and No debugger found" just RESTART (refresh) tag assistant on a page site.com/?gtm_debug=x, and you will see the effect! Good luck! i am from russia, sorry for my sentence and logic!)

Hi All,

I hope this comment will help some of you. It might be related to the comment made by Akim1337.
In short I couldn't preview my newly created and published container with a working tag (confirmed through GA dashboard) as I kept receiving "timeout" error in the Tag Assistant page and "no debugger found" in the previewed page. I believe I tried everything from the list in this post and please forgive me if my solution is there and I somehow missed it.

So solution first:
Remove Google Tag Assistant Extension from Chrome Extensions (disabling might help as well)

A bit more about the problem:
1. The new container features GA4 tags only
2. Container was implemented correctly and published with a basic Page View GA4 Event tag in it (I took a leap of faith not being able to test the first tag) - data flew to the property whcih I cinfirmed in Real Time report.
3. Any attempt to use Preview ended up with "0 container found" and "timeout" error in the tag assistant page and with "no debugger found" in the previewed page
4. Preview worked completely fine with other containers that contained GA3 tags
5. When Tag Assitant launched after hitting Preview button - the URL field just above the Start button was not populated with the URL of the page I was trying to test (which was the case for all the other containers)

All in all our IT suggested disabling all the extensions one by one and checking after each step if it has fixed the problem or not.
It worked after disabling Google Tag Assistant. If you have any suggestions for me to try and debug it further please let me know. Perhaps I missed some steps that would show it's a red herring - I am happy to help :)

Hi All,

Recently I had the most confusing experience, we were using zones to load containers in different apps and we also have a custom javascript variable to control what analytics property should receive the data, but because we had a zone restriction no tag was firing so if you are using zones make sure to check the zone restrictions because the assistant won't tell you if the tags did not fire because of zone restrictions

Another thing to try - this may just be coincidence - log out of admin on your Wordpress site. I kept getting "can't connect" errors whilst I was logged in as an admin. I logged out and it was ok connecting. May be coincidence.

Every time I visit to a new page on my website a new google tag manager installation appears on my Google Tag Assistant Chrome Extension.

I have not encountered this before. I am not sure what is going on. Has anyone else seen this?

just came to drop you a huge thank you, your guide was SUPER HELPFUL

Great post! I ran into the timeout problem described by several people in the comments. For me, the culprit was the DuckDuckGo privacy extension in Chrome. I disabled it and things worked as expected.

Hello. In my case with the GTM preview mode ON, it shows events in this GTM window (precisely in the GA4 container next to UA container) but not in Analytics GA4 DebugView

Just spent a fair bit of time reading through a few of your troubleshooting guides but haven't solved my problem yet. I have a site (and due to some nondisclosure, I can't link you) where we have GTM installed (I've checked for punctuation problems, looks fine), GA tracking installed in the GTM container, plus some other tags. No environments, nothing fancy on the GTM side. I am getting the "Message" instead of "Container Loaded" thing you describe here: https://www.analyticsmania.com/post/pageview-trigger-not-working-in-google-tag-manager/ but the solutions there have not resolved this issue. I AM pretty sure at this point that the data layer is broken in some fashion, but can't be certain.

The really weird thing here is that while I can't get Preview to even show me a container load, Analytics is reporting plenty of visits (albeit significant losses, without recovery, after a new site design launched in 10/2020). Clearly the GTM container is loading for SOME users, but not in Preview. I am also pretty sure that my visits are not being recorded in Analytics, ie this container isn't loading tags for me, ever, in Preview or just browsing.

Right now I'm trying to get someone to look at the data layer, which is way outside my area of expertise (I'm an SEO and Analytics person, but I don't use GTM terribly often and I'm not a coder), whether there might be CDN issues involved, and review an age-gate popup to see if that's blocking cookies being set.

Do you have any other suggestions or things I should be looking at?

I was having issues getting the new preview to work in GTM. I still had the old Google Chrome Tag Assistant Chrome Extension installed the website would not connect in GTM until I clicked the Chrome extension to enable that. Then the site would connect with the new GTM preview.

Once I removed the GTM Tag Assistant Chrome extension the GTM preview connected to site right away. It seems that extension no being enabled on the page was causing the GTM preview to not connect.

Hi, I have a single page application. With GA4 the page views are firing on some of the pages and then suddenly stop tracking at the last 2 steps of the checkout. I am using a nuxtRoute event trigger of a history event trigger. Nothing works. Any ideas. I also dont see anything else load into the GTM tag assistant.

Same problem as many here.
GTM's preview mode isn't updating tags and triggers unless the container is published as mentioned in solution #10
Another issue I have, is that everything is delayed: the same values for click classes sometimes appear and sometimes don't. The same goes for firing tags and triggers which appear with the red X cross (when checking variables in the preview mode) and a bit later the green mark appears.
Worse, sometimes a tag that was working fine then stops firing when used a minute later then works (back and forth). Isn’t this going to mess up my analytics ?
This is very confusing as I can spend time trying to fix an issue that actually wasn't one. What is this?
Thank you for your help.

I've resolved the issue. In the GA4 admin interface on web streams details. There is an enhanced measures option. If you go into this and show advanced measures on page views you can untick Page changes based on browser history events, which stops another history event firing. This appears as event gtm.historyChange-v2

Hi Julius,

Thanks for the blog!

I set up my GA through GTM for tracking. Also, GTM Code was inserted by the use of Magento. Now my Google Analytics records data when I apply a month range(That means GA is tracking data). The real issue here is, when I see real-time reports in GA and open my website in the next tab or on my cell phone I sometimes see myself getting counted as a real-time user, and sometimes GA doesn't count me as a user and shows zero number of the user. Now I am just skeptical about the reports I am looking at in analytics. There's no IP Filter applied in GA which is blocking it from tracking.

I have cross-checked my GTM and GA codes and they are configured correctly. Also, when I try to preview in GTM debugger it says not connected /time out error. I am just affraid is magento responsible for my GTM javascript code not loading properly in different browsers or something is blocking it from loading? (When I check my source code GTM head and body is present).

Thanks in advance. I will be glad if you could help.

Totally agree with the advice about Brave. I switched from Chrome to Brave a few weeks back because of the privacy issues. Quite happy with that. However yesterday I tried to test my various tags via GTM and Tag Assistant in Brave, and had huge issues. After trying Brave with shields down and various other work arounds, no joy. So, I went back to Chrome to do the GTM work, and all just fine. So, message is same as Julius's recommendation. Avoid Brave for any GTM work.

Great! My container wasn't published. Thank you.

Hi. Great post! Just wanted to share what I found.

After running through everything on this troubleshooting list, I finally figured out my connection issue was due to the Edge browser (Version 88.0.705.56 (Official build) (64-bit).

This morning, I woke up and thought to give Chrome a shot. Bingo!

For both Edge and Chrome and I have the same extensions running.

Hope this helps someone.

Thanks for this resource!

Sites can block GTM or other unknown js scripts from running via content security policy (CSP).

if you've followed all the steps and still aren't able to see GTM/preview mode work, ask your devs/webmaster/IT team whether or not your site has a CSP implemented.

if so, the following values may need to be added to the CSP properties:
script-src: 'unsafe-inline' https://www.googletagmanager.com
img-src: www.googletagmanager.com

and to enable preview mode, some further CSP properties need the following domains added:
script-src: https://tagmanager.google.com
style-src: https://tagmanager.google.com https://fonts.googleapis.com
img-src: https://ssl.gstatic.com https://www.gstatic.com
font-src: https://fonts.gstatic.com data:

I'll add another unexpected preview mode blocker...
If you're using Windscribe VPN's Chrome extension, it will somehow block the preview mode and cause a timeout error.

Thank You Mate! Really Appreciated.

Use two tabs to make it work. two separate windows of for example localhost:3000, while connecting to tag assistant.

Solution if none of the above worked!

Using Chrome Browser, check your Chrome Extensions. I removed any unnecessary extensions, including DuckDuckGo Privacy, EPUB Reader, McAfee and a few more and now it's connecting. So I'd suggest looking through chrome://extensions/ and seeing what you can remove to test it out.

Preview mode didn't work until I activated Tag Assistant Companion

Good luck!!
(sorry if it's repeated)

Thanks - worked for me!

My solution is to run VPN (for example in Opera). None solution in this article did not work for me. But VPN helped to connect to gtm.

Hello,

I'm a beginner in Google Analytics and Google Tag Manager, and I religiously followed the steps in your "How to Install Google Analytics 4 (with Google Tag Manager)" Youtube tutorial. But, when I click Preview, type the website URL, it shows "Not Connected" on top of the domain name on the upper left corner of the page, and below it, "0 Google containers found". On the pop-up, it says "Could not connect to the *domain name* and "Tag Assistant could not connect to a tag on *website url* - Retry button - "A timeout occurred while attempting to connect. Check that the page is tagged correctly and no errors have occurred." I tried the solutions listed here, except for #15 as I cannot comprehend how to do it, how to find the GTM code, and afraid that I might make a significant change to the website. Please help! Thank you so much.

I hope it's okay that I've posted the links here. If it exposes us to anything or anyone that would mess up our website or get access without permission, would you be kind enough to delete my comment once you've checked on the links? I'd really appreciate it!

For me it worked by simply using Google Chrome instead of Firefox. Funny how I needed to google my issue before even thinking about that solution, but then again, why the hell shouldn't it work in Firefox *drunk smiley*.

Seriously need some help! I'm working on this website https://[REDACTED].com/ and I've put in the GTM tag using headers and footers wordpress plugin. When I try to use preview mode it opens in a new tab (which is an improvement because last week it was opening in a new window). But the preview mode badge after trying to connect says "No debugger found." The tag assistant page says "Tag Assistant could not connect to a tag" and "A timeout occurred while attempting to connect." I have checked using the legacy tag assistant extension that the overall GTM tag is there (although I still don't see my tags & triggers firing).

https://tagassistant.google.com/#/source=TAG_MANAGER&id=GTM-5DB2LP4&gtm_auth=28vEPnx1MoQvdvXzEjs_Xg&gtm_preview=env-5&cb=4868435366233155

Greetings! This is more of a "connectivity" issue. I'm sharing my recent solution in case others experience the same challenge.

For the longest time, I was being disconnected from the GTM debugger after several minutes of previews and tag tweaks.

For no reason (that I could find) I got a dropped connection and the message "lost connection to the page being debugged". No other lost connections, like wifi etc.

I "unabled" all Chrome extensions, even uninstalled (as suggested in an earlier post here) the Legacy Tag Assistant and installed the Tag Assistant Companion extension. Nothing worked.

On a whim (how's that for critical thinking?) I "unabled" the Tag Assistant Companion. And it worked!

It's now been several hours and no dropped connection. One side note: now the site page being debugged shows up in its own Chrome window, whereas before it was in a tab alongside the debugger tab and GTM tab.

Go figure!

PS: if anyone can shed light as to why this may have been happening and why this solution now works, please share. TIA.
Tom

Greetings again! Please ignore my last post - after several hours of connectivity, started testing some existing tags and within minutes, got dropped.

So I'm back to the community - what's happening here?

Tom

Hi,
For me, what solved the problem was disabling the Tag Assistant extension on my Chrome browser.
After being so desperate for a solution, I just tried randomly(ish) "solutions" until I thought about it. Just that!
I hope it helps
Thanks for the many tutorials

hi Julius! could you please take a look at my case?
I went through on the 20 points, and can not figure out why my preview mode is not connecting. It launches the website correctly, but the debugger can not connect, and gives a "not connected" status.
Here is the preview link:
https://tagassistant.google.com/#/source=TAG_MANAGER&id=GTM-MBQFRPK&gtm_auth=ip1tTwDqg4UeCkDV6Mcezw&gtm_preview=env-8&cb=5613656775971035

thanks!

Hi Julius

Thank you for the great post. I've tried your solutions, but none of them works for me. I'm trying to debug the site https://thehungerproject.se/ but it won't connect. Could you please take a look?

This is the tag assistant-link: https://tagassistant.google.com/#/source=TAG_MANAGER&id=GTM-P97SV3D&gtm_auth=QAsXFhoWGk2HYHw3IL6X6A&gtm_preview=env-8&cb=8561245460848193

Thank you.

Hi Julius, I am facing an issue.
GTM tags are added in all the pages of the website. I added some tags and set the trigger on Thank You page.
So on preview mode when I do a test after all the steps and reach thank you page tags are not getting fired. The Thank you page remains for 10 sec and then take back to home page. Is this causing the issue. Because when I click on back button, it takes me again to thank you page and when I refresh the pages, tags got fired but now thank you page remains no taking back to home page.
Hope you understand the problem. I am not able to debug it.

Hi everyone. In my personal circumstances NOTHING here worked. On the brink of giving up, I then remembered I have the "Malwarebytes" extension installed on Chrome! That was blocking not only the Tag Assistant debugger, but also Google Analytics itself! (on the Site/page I was trying to debug).

Enabled / white-listed both on that Site in question... *bingo!* - it worked. MAN I lost several hours reaching this point...!!!

The Preview mode wasn't working for me. After some investigations, I found out that gtm.js was being blocked by the uBlock Origin Google Chrome extension which I had installed in my browser. After disabling this extension, the Preview mode works.

I have a single page website (react). For anyone using react / node.js or .net core, the languages are natively designed to prevent injection scripting (which GTM requires), so you should run the react module which solved the problem for me:

https://www.npmjs.com/package/react-gtm-module

@Suraj - running the module worked for you because react is designed to prevent injection for security.

Thanks for your help!

My Ghostery extension was the problem for me.

For me it started working as soon as I disabled Site Kit plugin (wordpress).

It worked on Wordpress when I logged out of my wordpress admin

Thank you. #1 worked for me. I can't get the preview to connect using GTM, but I can using the Tag Assistant plugin.

Thanks! I was trying everything to get it working and it was #8 for me.

I checked in every manners, but tag preview is not connecting the site.

when you use Tag Manager’s preview mode, you will now see two windows: a Tag Assistant window, and the window that you're testing. We’re continuing to improve the experience and introduce new features to help you do even more to debug your containers and improve your tagging.

My question is
Now is it different the way does it work? You'll get two windows instead of the orange frame.

https://support.google.com/tagassistant/answer/10042782

You're a genius.
It was #12 for me.

Going through a strange issue currently when using Preview mode where both windows are closing out of nowhere that I hope you can help with...

When I visit the URL page it closes the window completely so there must something wrong with my website as it seems to be able to close the GTM-debugger and GTM-account tabs on my browser after navigating to the URL.

Normally the GTM-debug view just doesn't give updates on the new page if it isn't connected but I have never seen it close itself AND the corresponding GTM-container page (non-debug view).

Video in URL....

If you have any ideas they would be most appreciated!

Thank you, for me the issue was the extension "uBlock Origin". After disabling, it worked.

My GTM preview is not working since 5 day, the full setup is the same and when I try the same GTM tracking on another Domain it works fine. Even Google Tag Assistant cannot read anything on this site (when I do inspect I see the Code added from GTM) but Google Tag Assistant cannot recognize it, but when I used the same tracking Code on a different site the preview works fine and even Google Tag Assistant see GA and GTM and Google remarketing and it shows all the connections were done perfectly. It is like this site or domain is preventing GTM and the Assistant to read it is source Code. Any idea what is the reason for this or how I can resolve this issue?

Hello, MY GA has drooped to 10% of traffic and my GTM preview is not working for 5 days, the full setup is the same and when I try the same GTM tracking on another Domain it works fine. Even Google Tag Assistant cannot read anything on this site (when I do inspect I see the Code added from GTM) but Google Tag Assistant cannot recognize it, but when I used the same tracking code on a different site the preview works fine and even Google Tag Assistant see GA and GTM and Google remarketing and it shows all the connections were done perfectly. It is like this site or domain is preventing GTM and the Assistant to read it is source code. Any idea what is the reason for this or how I can resolve this issue?

GTM Preview works for everything except for YouTube videos embedded in modal popups. Upon inspecting the popup, the GTM attributes are injected in the code, but "YouTube Video" does not display in the GTM summary pane when the video is played. This applies to Chrome and Firefox browsers.

Hello All,

I have placed GTM code snippet as suggested but in preview it's not connecting to our webpage. We have build our webpage with IBM BPM tool. When I check developer's tool in chrome I can see message which is constantly printing.

com.ibm.bpm.coachflow.engine.ClientInterface.receiveEvent: Ignoring event from untrusted origin: "https://tagassistant.google.com"

coach task does not have an event binding for each outgoing link.

Anybody else ever have this issue?

GTM debug is no longer working as of Friday 30th July. It just won't connect. It says it is working on the web page but not in the debugging window. Have tried using the extension as well but have the same issue.

There were no changes on my website between when debug was working and now isn't working so a little puzzled.

I am seeing the following error in the dev console which is coming from the GTM debug bootstrap script:

Uncaught TypeError: Event is not a constructor
at I.setState (bootstrap:19)
at Jc (bootstrap:57)
at a (bootstrap:76)

My container has no changes in it and have tried previewing old versions as well and still get this issue so doesn't appear to be connected to any custom tags etc.

Any ideas??

https://tagassistant.google.com/#/?url=https%3A%2F%2Fwww.darwin-insurance.com%2F

Sorry think you need this one.

It's driving me mental, I reckon it is something so obvious!

https://tagassistant.google.com/#source=TAG_MANAGER&id=GTM-N6VX2P2&gtm_auth=0vOo9FdqSKjkU_fnAiT8xg&gtm_preview=14&url=https%3A%2F%2Fwww.darwin-insurance.com%2F

Apologies if this question has been asked before (I'm time-poor and stressed to figure out a solution).

GTM Preview Mode works fine, yet when I test out a trigger on a website I'm working on by filling out my details and clicking the submit button on a form, it is sending through an actual form.

I thought preview mode didn't action anything in real-time?

Hey there! THANK YOU SO MUCH - I was having such a hard time getting mine to connect because of a "Timeout" issue between the two, and it still was not working after I whitelisted and paused GTM, the tagassistant, and my brothers' site through Ghostery - but I figured I'd try connecting in an incognito window because I have quite a few extensions, AND IT WORKED!!

EFFING MALWAREBYTES, MAN.

Within the Malwarebytes Browser Guard extension, I had to not only pause ad-blocking {that I didn't realize it was doing for me), but I had to pause ALL "Browser Guard" activity, and that finally helped.

Please mention this in the next update you do, I'd love for this to help someone ahead who's also using MalwareBytes Browser Guard extension.

Again, thank you.

Many thanks. Tip # 7 worked!

The Cloudflare was configured to show cookie acceptance popup and this blocked the work of gtm.js. After disabling popup, the situation was corrected.

Here's what worked for me: Export workspace, Import to new workspace, Delete original workspace. For whatever reason, GTM Preview just didn't like that workspace I was in but was fine with everything else.

Hi, I was trying to create an ads conversion tag to track the clicks on my phone link on a custom event trigger (no previous tags have been configured) Everything was working as expected, I could see the tag being fired in the debug mode and on the tag manager legacy plugin, and I was able to configure and publish the tag. But suddenly the debug and preview mode stopped working. I get 6 summaries -> message, consent initialization, initialization, container loaded, DOM ready, and window loaded. But nothing appears after that when I click on any link. I have followed the advise from yr post. I have not made any changes to the website. I have tried publishing container. I have closed all windows containing the tag manager. The container name is correct. I tried unchecking the query parameter. But nothing I do can make the messages work in the debug mode again. Please advice.

Hi, i don't know if this falls into the category of Preview mode not working. I just got access to this GTM account. Tags and triggers are there=>https://tinyurl.com/yg65jexe

However, they don't appear in the preview mode. Only the Pageview tag works=> https://tinyurl.com/yjxppg5g

What's weird is that some do work and appear in GA... any idea? I also just created a quick trigger and its not showing up in the preview mode. thanks so much.

Hi there,
I've followed your instructions, but still it is not working properly. Sometimes when I just enter the preview mode, then it looks like it's working for a really short period of time. But then after some moments, it says 'Can't connect to the website.'
Really strange...
Would be great if you could help me out.
Kind regards,
Boudewijn

Hi there,
Thanks for the blog, but for me, it seems that my tags are working fine over on the preview mode but I can't see them on the live website. Even when I have already published the container. The GA pageview tag is working in preview mode but can't be seen on the live website.

If you import the script with a dynamic import, the CSP will prevent the preview mode from working, but the browser will not warn you in the console.

See this page for CSP policy for GTM, GA, and other google products: https://developers.google.com/tag-platform/tag-manager/web/csp

HI

I added page view event and FB pixel helper shows
"The Facebook pixel activated 2 times on this web page, which can cause errors in your event tracking."

How can I resolve this?

Hello Julius,

I'm getting the following on some sites that I'm debugging:
Status: (blocked:other)
Type: script
Initiator: (index);244

Disabled all extensions, using latest version of Chrome.

Hey, after reading your blog completely I'm still facing issues. In my preview mode only two containers are there UA and G-. The website belongs to my client and I've installed GTM code properly but UA and Ga4 is already installed in my clients website and now whener I debug, there are only two Google cotainers found UA and G-.
Can you please help me.

hi
I have read all the problems and answers and didn't find any similar to my. Tag Assistant and Tag Manager don't want to connect to my site from Chrome and Edge browser but on my friend's laptop can connect.Global Site Tag and Tag Manager and Facebook piksel are added correctly to my site.
Tag Assistant returns errors :
An error occured while the tag was fired: net::ERR_CONNECTION_REFUSED
Error while sending request: net::ERR_CONNECTION_REFUSED
Invalid or missing account ID
As I said on another laptop there are no problems at all, there must be something wrong with my comp.

excellent information, thank you very much, but don't go against my mistake, my tag assistant can't find my GTM, it only shows me my GA4 and I don't know what to do.

Hi.
The tags I have created are getting fired in the preview mode. The cookie is also created which is visible under applications tab under developers tool, but do not set. The cookie is visible for a few seconds and than automatically get removed from the cookie list. Please suggest any resolution.

Thank you in advance

Hi,

GTM is not working in my environment, but other environment it is working fine. getting this error is console.

GTM id used same in both.

qa: "Uncaught TypeError: Cannot read properties of undefined (reading 'length') - :2"

Hi
After creating the tag, (CTA-button) for example, when I previewed it, it gave an error and it was placed in the not fire section. When I refresh again, it goes to fire section and when i refresh again too; the tag goes to not fire section and does not show the green or red tick marks in the preview section.
how can i solve this problem?
thank you

Hi Julius,

Thanks for such an extensive list of issues for GTM's preview & debug.

Wondering if you have come across this issue - "Not enough memory to open this page".

I kept getting it upon submitting a (few) form(s) for testing. I've tried both Chrome and MS Edge with the same outcome.

I've got a "not connected" in red, in the upper left hand corner above the URL domain after running the the preview mode. I worked through all your blog suggestions but still no luck. Any idea what I'm missing?

Thanks for your help!

Hi Julius -- This isn't a Preview/Debug issue exactly. We are using a javascript serverside geo redirect that redirects traffic from example.com/home.geo.html to the appropriate country version of our home page based on the visitor's IP location (so destination URL could be example.com/uk/home.html for example). When we implemented this we didn't consider whether our tags (many of which are set up in Tag Manager to trigger domain-wide) would fire when people hit this redirect URL (example.com/home.geo.html). And of course, when I try to see what tags may be firing there using the Preview function, that URL just redirects to the destination URL, so I can't tell. My belief is the redirection happens too fast for any tags to fire. Do you know if that is true? Or do you know any way to see what tags may be firing before the redirect occurs? Thanks in advance.

I was using Safing's Portmaster and SPN, and that was blocking GTM and my connection was timing out.

Once I deactivated that, I was able to connect GTM and preview my container on the site.

Hello, one of my clients had his tag manager installed on a website but recently we found that the container snippet code that he was working on (and as he says, it worked perfectly fine) was replaced. He deleted the code and changed it to the previous container snippet. Now I am trying to use a debug mode and non of the methods work. What might be the issue here?

This is the preview mode URL: https://caru.ge/?gtm_debug=1669804746704

hello, first of all thank you for your tutorials, they have always helped me a lot. Now, I have a different error. It connects me to the page, but there is a form submission event that although it doesn't cause any error in the console, it causes the tag manager page to break.

Hi, I've got strange problem on the site I manage. After I installed GTM it's working only for logged users, after log out there aren't any container of ads. Site is in Wordpress. https://najlepszy-ranking.pl/