Problem: On Android my app's icon appears to be a simple box when receiving Push messages
Status Bar Icons on the Android system are composed simply of white pixels on a transparent backdrop, with alpha blending used for smooth edges and internal texture where appropriate.
If you provided a completely opaque icon for your app - the generated Status Bar icons will also be completely opaque. This results in the Status Bar icon looking like a completely opaque box, rather than a nice cut-out of your game's logo or icon.
To resolve this you will need to modify your game's assets, and update the status bar icons. The exact icon Android will use varies by display density - there are 4 different directories that will need to be updated. drawable-xhdpi-v11, drawable-hdpi-v11, drawable-mdpi-v11, and drawable-ldpi-v11. Please see the Android Developer's UI Guidelines on Status Bar Icons here for more information and design guides.