Guide 26 · Debugging · GA4 + Tag Manager
Events went missing after a site redesign: the tags stayed, the page changed
A redesign changes class names, page paths, and button text — and every trigger that matched the old page stops matching. Check the new page against the old triggers, one condition at a time.
After the steps below, every broken trigger is named against the new page, the triggers are updated to match, and the events fire again in Preview.
Download the check: the debugging check (JSON) (MD5 dfff0fb4d88fc211c4804b5628c72d2f, 486 bytes). It lists the checkpoints from this guide and the worked check, with the figures recomputed. The file was built for this guide and validated structurally — it was not exported from a live container or a live property.
What you need
- The list of tags and triggers from before the redesign. Export it, or write it down from Tag Manager, before anything is changed.
- The new pages, open in Preview. Tag Assistant connected, so each trigger can be judged against the new page.
- The old page paths and button labels. What the triggers used to match, so the new page can be compared with them.
- The data layer pushes on the new pages. What the new site pushes, and when — the redesign may have changed those too.
The trace
The worked check: the figures below were recomputed before publication, and the note under the table shows the working.
| Check | Figure |
|---|---|
| Tags in the container | 9 |
| Tags that fired on the new pages | 5 |
| Tags that did not fire after the redesign | 4 |
| Broken triggers that matched old class names | 3 |
| Broken triggers that matched old page paths | 1 |
| Tags firing again after the fix | 9 |
Nine tags were in the container and 5 fired on the new pages, so 9 minus 5 is 4 tags that stopped. Of the 4, 3 matched old class names and 1 matched an old page path — 3 plus 1 is 4, the whole gap. After the fix, 9 of 9 tags fired again.
- Count the tags that fire on the new pages. Start Preview, click through the new site the way a visitor would, and count which tags fire. In the worked check, 5 of 9 fired. Write down the 4 that did not — those are the broken ones, and the list is short enough to fix one at a time.
- Read the failed condition for each broken tag. In Preview, select the event and click each tag under Tags Not Fired. Preview names the condition that did not match. In the worked check, 3 failed on a class name and 1 on a page path. The failed conditions are the fingerprints of the redesign.
- Compare the old condition with the new page. Open the trigger and read the condition, then look at the new page: the button that was class buy-now is now class buy_now, and the page that was /checkout is now /checkout/confirm. The trigger is not wrong in itself — it is waiting for a page that no longer exists.
- Update the trigger to the new page, and check the data layer too. Change the condition to match the new class name or the new path. Then check the data layer: a redesign often renames the event push as well, so a Custom Event trigger waiting for purchase may need the new event name. Update both, or the tag will still not fire.
- Test every broken tag again in Preview. Repeat the actions for all 4 tags in one Preview session. All 9 tags should now fire. Then publish the version, and test the live site in a clean browser — the redesign changed the live site, so the live check matters more than usual.
Dead ends
DEAD END — REBUILDING THE TAGS FROM SCRATCH. The tags are fine; the page changed underneath them. Deleting and rebuilding 9 tags throws away working configuration and creates new chances to mistype the Measurement ID. Fix the 4 trigger conditions and leave the tags alone.
DEAD END — FIXING THE TRIGGER AND FORGETTING THE DATA LAYER. A trigger that matches again still fires nothing if the data layer push it waits for was renamed in the redesign. A Custom Event trigger and its data layer event are a pair — update both, and test both.
DEAD END — TESTING ONLY THE HOME PAGE. A redesign touches every page, and the break is often on one template only — the product page, the checkout, the form. Click through every template that carries a tag, not just the home page, or the broken tag on the last template stays broken.
End state
All 9 tags firing on the new pages, the 4 broken triggers updated to the new class names and page paths, and the version published. The redesign changed the page; the tracking now matches the page that exists, not the one that used to.
Sources
- Tag Manager Help — Preview and debug containers — Preview and debug mode showing which tags fired and what did not trigger a firing, for each event on the new pages
- Analytics Help — Monitor events in DebugView — DebugView as the check that GA4 receives the events once the tags fire again
Checked 11 November 2026. The click paths above are the ones in Google's help pages, opened 11 November 2026. What was run: the redesign counts, recomputed — 9 tags, 5 firing and 4 not, with 3 broken by class name and 1 by page path, and 9 of 9 firing after the fix. No step in this guide was run inside a live Analytics property or a live Tag Manager container, because both need a Google sign-in and this site does not sign in as anyone. Google moves menu items without warning; if a path on this page no longer matches, the linked help page is the current map.