“4. Watch out for Android App errors

To help you identify errors when indexing your app, we’ll send you messages for all app errors we detect, and will also display most of them in the “Android apps” tab of the Crawl errors report.

In addition to the currently available “Content mismatch” and “Intent URI not supported” error alerts, we’re introducing three new error types:
APK not found: we can’t find the package corresponding to the app
No first-click free: the link to your app does not lead directly to the content, but requires login to access
Back button violation: after following the link to your app, the back button did not return to Search results.

In our experience, the majority of errors are usually caused by a general setting in your app (e.g. a blocked resource, or a region picker that pops up when the user tries to open the app from Search results). Taking care of that generally resolves it for all involved URIs.” http://googledevelopers.blogspot.com/2014/12/four-steps-to-supercharge-deep-linking.html