If you see very little or no AdSense data in your Analytics account, and you've already linked accounts, review the issues below to find out what might be the cause.
If you haven't linked accounts yet, review Link your Google Analytics 4 property with AdSense and the Linking AdSense and Analytics FAQs.
Have you linked the correct Analytics account?
In your AdSense account, visit the "Manage your Google Analytics links" page, and check your Analytics links. Or, in your Analytics account, check your links under Admin, then Product links, and then Google AdSense Links.
If you've linked the wrong Analytics account, unlink accounts and re-link to the correct account.
Have you placed the Analytics code on all of your AdSense pages?
Check to ensure that the Google tag is set up correctly on your site(s). Your GA4 web property must be configured to collect data using the Google tag.
Did you link accounts more than 24 hours ago?
After you link accounts, it can take up to 24 hours before data is collected.
Are you comparing your Analytics data to AdSense for content ads data?
AdSense reports in Analytics only track AdSense for content ads. When generating a report in your AdSense account, make sure that you select AdSense for content as the product. This will ensure you're comparing the right data.