I’ve been waisting some hours by hunting a stupid “bug”:
I am using Android Studio and was following the “Maps SDK for Android > Getting Started” guide. Of course I also ran into the issue of a wrong API key. But this was all solved by Googling and StackOverflow.
The map still showed up in the Emulator but NOT if deployed as stable release into the (beta) release channel to the PlayStore! LogCat was also silent … After a while I realized thetiny hint in AndroidStudio: