The most common reason this occurs is that even though you created the GA4 property and connected it to your dashboard, the GA4 tag isn’t collecting analytics from your site.
Follow these three steps to resolve this issue
1. Ensure your GA4 property is fully set up in your Google Analytics dashboard.
Go to the admin section of your GA dashboard, look under the Data Collection and Modification column, and then select "Data Streams":
You would normally expect to see a status that says “Received traffic in past 48 hours”, but if your GA4 tag isn’t passing data as expected you might see “No data received in past 48 hours”, "Data Not Flowing" or "Not Started".
If you are seeing a flag like this in your Grow Publisher Portal -
But your tag is showing that traffic has been received in the past 48 hours, make sure you’re looking at the correct GA4 tag in Google Analytics.
2. Ensure your GA4 property's data stream has been set up
If the status says “No data received in past 48 hours”, click on the arrow next to the Data Collection status. On the Data Streams page, click on the arrow next to your data stream and then “View tag instructions”.
Note: if you don't see this screen and instead see a screen asking you to select a platform, that means you need to set up a data stream. Just select Web, enter your domain and site name, and click "Create stream"
3. Follow the instructions to add this GA4 property's code to your site
Next, look at the recommended instructions on how to add this GA4 property to your site. This is a crucial step since this is how the GA4 property collects data.
Click "View tag instructions" and Google will give you a couple of options on how to get the code added to your site. If you're unsure of which approach is best, click on "Install manually" and copy the script into the head of your site:
Once the code has been added to your site, allow up to 24 hours for data to filter into your Grow Publisher Portal / Journey Dashboard.