After placing code for automated AdSense ads, ads are not shown and a warning appears in the browser’s toolbar: No ad placements found for publisher ID ‘ca-pub-123456789123456’. Check that the provided publisher ID is correct. Most likely you are trying to see ads from non-supporting devices on AMP pages.
Open the AdSense help and see the warning:
- Amp Auto ads will currently only show for users using a mobile device. Please test your site in a mobile device to see AMP auto ads.
But just in case, check whether the client identifier is correctly specified (in the example: ca-pub-123456789123456) and all the code for automated announcements for AMP:
<title>My AMP Page</title>