Compilated on cocoonio project perfect work with installing debug apk version, show ads and runs. But signed release not show any ads. I will give two apks, debug and singed release to you can check, work on it two days cant fix it.
Zip with two apks:https://drive.google.com/open?id=1WGbm3uqbdqnwGU7Obu78HSxrdwpLIAmn