First: i recommend you to join official discord, you will get way better and faster answers than here.
For your question:
Are you using an emulator? If yes, that is the problem (if not, please record it and post on discord that way we could help you).
There is a bug with some emulator configuration that makes this occur, and devs will not adapt it every emulator's updates. As far as i read until now, it seems android 5 on Nox is working without this problem. Please join us and ask again if you still face trouble or to find someone with solution ;)
From what i know, ads aren't a problem from the game, it is a google problem. If you are seeing 'preparing ads"', i understand it is "ask one more time". If it keeps happening, check your google play or apple store account, or somth like that, or maybe it is a connexion problem. I cannot tell more than that from what i know sorryAds error 1