Consent Mode blocking all measurement: telling it apart from a bug

You deployed a consent banner and Consent Mode — and conversions suddenly stopped. Before treating it as a bug, you need to separate two things: it might be correct behavior (users declined), or a setup error blocking even what should come through.

First: is it even a bug?

If you use basic mode, it's expected that nothing is sent without consent. So a drop in measurement after deploying the banner isn't necessarily a bug — some users simply won't consent. Check how many users consent before hunting for a technical problem.

Common real bugs

• Missing default state before tags. If you don't set the default consent state before tags load, behavior is unpredictable.
• The banner doesn't send an update. The user clicks "I agree" but the CMP doesn't send a consent-state update — tags stay blocked even though consent was given.
• Wrong load order. Tags fire before the consent signal arrives.
• Consider advanced mode. In basic mode you lose data from those who decline. Advanced mode sends a cookieless ping and enables modeled conversions.

What to check

• In GTM preview mode, watch the consent state — is the default set, and does an update arrive after consent?
• Test measurement with and without consent and compare behavior to what you expect for your chosen mode.

How to set up Consent Mode v2 correctly and the difference between basic and advanced mode is explained in Consent Mode v2 and server-side GTM: GDPR in practice.