Stating the obvious, but also make sure you have not silently messed up the reference to the applicationId
in android:authorities
.
In my case I made a typo and omitted the damn dollar sign :
android:authorities="{applicationId}.myprovider"
instead of :
android:authorities="${applicationId}.myprovider"
That did not cause any immediate error (since it is a valid authority name). But a couple days later, when I tried to install different variants of an application, it was a real pain to understand what was wrong, as the error message does not give much info about what is wrong with the content providers.
Another way to troubleshoot this is to compare your merged manifests, looking for identical authorities.