Error when implementing admob in android application

hello, sorry for the question but I followed a tutorial to the letter and I do not appear ads admob in all its varieties (banner, Interstitial and video reward) and nothing. compile it locally as in the compilation option offered by the same gdevelop and nothing. Someone can tell me what I did wrong. I leave the link of the video I used to implement the admob

admod tutorial

Some times ads come up late. Because they work according to the ad campaigns (ad provider) they get.
Can you please tell on what platform you uploaded the game? It should work on google play store.