A form gets filled in, a sale goes through, and GA4 shows nothing. The cause is almost always one of a short list. Work through it in this order, and test each fix before you wait for the reports.
First: test it properly
Standard GA4 reports can take 24 to 48 hours to process data, so don't judge a change by them. Use the Realtime report, or turn on debug mode (the Tag Assistant browser extension does this) and watch DebugView in GA4 while you complete the conversion yourself.
The nine common causes
- The event never fires. A redesigned button, a new form plugin or a form that submits without loading a new page breaks the trigger. Check the event appears in DebugView when you convert.
- It fires but isn't a key event. GA4 now calls conversions "key events". The event has to be marked as one in Admin, and its name must match exactly; event names are case-sensitive.
- The thank-you page isn't reliable. Some visitors reach it without converting, others never see it because a payment page or redirect skips it. Fire the event on the action itself where you can.
- Consent switches measurement off. Without Consent Mode, visitors who decline cookies send nothing. With Consent Mode v2 in advanced mode, Google can model those conversions.
- Checkout happens on another domain. When the sale completes on a payment page or a separate shop domain, the session breaks and the sale is credited to the payment site. Set up cross-domain measurement and list payment providers as unwanted referrals.
- Two tags count the same thing. GA4 installed in the page code and again in Tag Manager counts every event twice, so the numbers look wrong rather than missing.
- A filter removes real traffic. An internal-traffic or developer filter that is set too broadly can drop real visitors. Check Admin, Data filters.
- Ad blockers and browser privacy. Some visitors block analytics entirely. Server-side tagging reduces the loss, but a share of visitors will always be invisible.
- Google Ads isn't fed. Google Ads only sees GA4 key events after the accounts are linked and the conversion is imported and set as primary. Otherwise bidding learns nothing from it.
How Hong Kong companies do
In our November 2026 study of Hong Kong companies listed on HKEX, 46% of websites ran GA4 and 14% had a Google Ads tag. 16% still loaded Universal Analytics code, which stopped collecting data in July 2023.
Check yours in a minute
Our free Tracking Check shows whether GA4 and the Google Ads tag are installed, whether conversion tags exist in your page and your Tag Manager, and whether Consent Mode v2 works.
Frequently asked
How long does GA4 take to show conversions?
Standard GA4 reports can take 24 to 48 hours to process data. To test a change, use the Realtime report or DebugView instead of waiting for the reports.
What is a key event in GA4?
Key events are what GA4 used to call conversions: the events you mark as important to your business, such as a form submission or a purchase. Google Ads conversions can be imported from them.
Why does Google Ads show fewer conversions than GA4?
They count differently: Google Ads credits the ad click within its own attribution window, while GA4 can credit other channels, and only key events you import into Google Ads appear there. Missing Consent Mode signals widen the gap.