(Bad english) I had the same problem and I solved it by using latest build of godot 2.1.5 but remember that your game must be exported using godot 2.1.5 not 2.1.4. Godot engine 2.1.5 is in beta but I didn’t have any problem using it.
This is the game that I made: https://play.google.com/store/apps/details?id=com.kuaper.centereffect