Why your GTM container isn't loading at all
When Google Tag Manager itself fails to load, every tag inside it goes dark at once: GA4, your pixels, conversions, all of it. Before debugging any single tag, it is worth confirming the container is even loading, because that changes the whole diagnosis.
How to tell the container is the problem
If one tag is misbehaving, that is a tag-level issue. If everything stopped at once, suspect the container. Open GTM Preview: if it cannot connect to your site at all, or the gtm.js request fails in the Network tab, the container is not loading.
The usual causes
- Snippet missing or malformed: the GTM code was removed in a redesign or only half-pasted.
- Wrong container ID: the site loads a GTM-XXXX that is empty or belongs to another property.
- Consent tool blocking GTM itself, not just the tags inside it.
- Content Security Policy blocking the Google Tag Manager domain.
- Ad blockers, which also stop GTM from loading for some visitors.
How to fix it
Confirm the exact GTM snippet is present in both the head and body, with the right container ID, on every page. Check it is not gated behind consent in a way that blocks the container entirely. Check your CSP allows googletagmanager.com. Once gtm.js loads cleanly in the Network tab and Preview connects, move on to the individual tags. A publish that broke tracking is a related but separate failure.
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