We learned in December that Google was updating their app-indexing crawl errors within Search Console, along with the app indexing docs. Google has now announced exactly what the changes are.

While two of the Android app indexing crawl errors shown Google Search Console remain the same (Package not found and URI unsupported) there is a brand new error now being displayed – Removed from index.  This error is for app indexing pages that Google has removed for technical reasons.

All about the new error type
These are app pages that don’t meet our technical guidelines — for example, users get redirected to the home page or the app crashes when the user attempts to open the deep link.

To fix this, check the example URIs both in Fetch as Google and on an actual device, and make sure your app doesn’t crash on opening, the deep pages don’t redirect to the homepage, and the content is equivalent. Once you fix the issues and we recrawl your app pages, these deep links from Google search to your app will be reexamined.

Google has reset the app indexing data, so you will be able to see the new error retroactive to December 11th. It should be active in Google Search Console now for all users.