Why did GA4 stop collecting data after I added a cookie banner?

Almost always because Consent Mode is denying analytics_storage by default and never updating it — so Google tags stay blocked and no events are sent. The fix is to make your consent banner pass and update the consent signals correctly, and ideally run Advanced Consent Mode so cookieless pings still flow.

How do I know if Consent Mode is blocking my events?

Use GA4 DebugView or the browser's network tab: if requests only fire after you click 'Accept', consent is gating them. If they never fire even after accepting, the banner isn't updating the consent state. Google's Tag Assistant shows the consent state on each tag.

Consent Mode Is Blocking All My GA4 Events — How to Fix It

Q: Should analytics be blocked before consent?

Under GDPR, non-essential analytics cookies require consent, so blocking cookie-based collection before consent is correct. Advanced Consent Mode is the middle ground: it sends anonymous, cookieless pings before consent so you still get modeled data without setting cookies.

You added a cookie banner for compliance, and GA4 went quiet. Sessions cratered, purchases stopped showing. This is one of the most common GA4 failures on Shopify — and it’s almost always Consent Mode denying by default and never updating.

What’s happening

Consent Mode gates Google tags on a consent state (analytics_storage, ad_storage, and the v2 signals). A correct setup:

Defaults to denied (compliant), then
Updates to granted the moment the user accepts.

The broken setup does step 1 but never does step 2 — so tags stay blocked forever and no events are sent, even for users who clicked “Accept.” It looks exactly like a tracking outage.

Diagnose it in 2 minutes

GA4 DebugView / Realtime: do events appear only after you accept — or never?
Browser network tab: filter for google-analytics / collect. Do requests fire on accept?
Google Tag Assistant: it shows the consent state on each tag firing. If analytics_storage stays denied after you accept, your banner isn’t updating consent.

If nothing fires even after accepting → the update step is missing or misfiring. That’s the bug.

The fix

Make your CMP send the consent update on accept (and on decline). Most Shopify consent apps / CMPs (e.g. Google-certified banners) do this — check it’s actually wired to Google Consent Mode, not just hiding cookies visually.
Set sensible defaults, then update — don’t leave everything hard-denied with no path to granted.
Run Advanced Consent Mode so that even before consent, anonymous cookieless pings flow and Google can model the rest (see does Consent Mode hurt conversions).
Re-test in DebugView until events fire (modeled or granted) instead of vanishing.

The goal isn’t to bypass consent — it’s to stop a misconfiguration from zeroing out your data. Compliant collection and working analytics aren’t mutually exclusive.

After the fix

Reconcile a closed period against Shopify. If GA4 is back within a normal 5–10% gap, you’re good. Still missing purchases specifically? Check the purchase event separately.

FAQ

Why did GA4 stop after I added a cookie banner? Consent Mode is denying by default and never updating to granted, so tags stay blocked. Fix the update step and consider Advanced mode.

How do I know consent is the cause? DebugView / network tab / Tag Assistant — check whether events fire on accept and what the consent state is.

Should analytics be blocked before consent? Cookie-based collection, yes. Advanced Consent Mode sends cookieless pings before consent so you keep modeled data.

Sources

Google Ads Help — About consent mode
Google — Consent mode + Tag Assistant / debugging
Cookiebot — Consent Mode v2