Tag not firing in GTM? A step-by-step diagnosis

A tag that refuses to fire in GTM is almost always one of five things. Work through them in this order and you’ll find it quickly, instead of changing settings at random.

1. The trigger isn’t matching

Open GTM Preview and do the action that should fire the tag. If the tag shows as not fired, click it to see why: usually the trigger condition didn’t match. A common culprit is a trigger looking for an exact value (a URL, an event name) that differs slightly from reality, a trailing slash, a capital letter, a different event name than your dataLayer actually pushes.

2. An exception or blocking trigger

A tag can have a trigger that fires it and an exception that blocks it. If both are true at once, the exception wins and the tag stays silent. Check whether a blocking trigger (often a consent or page exclusion) is catching the case you’re testing.

3. Consent is holding it back

If the tag has consent settings or your setup gates tags on consent, it won’t fire until the matching consent is granted. Firing for you after you accept but not before is consent doing its job, not a broken tag.

4. The dataLayer is missing the data

• The event the trigger listens for isn’t actually being pushed to the dataLayer.
• The tag fires but the variables are empty, because the dataLayer doesn’t contain them (common on ecommerce events).
• The dataLayer push happens after the tag would need it, a timing problem.

5. You didn’t publish

Last but commonest of all for live issues: it fires in Preview because that’s your draft, but the change was never published, so the live container doesn’t have it. Submit and Publish, then retest live.

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