When the game is compiled and run on Android, the ADS does not appear

I created the various scripts and followed the Unity guide step by step, and it seemed to work in the Unity window, so I deactivated the test mode everywhere and compiled the game and ran it on my smartphone, only that once I ran it, the advertising didn’t appear. appeared, and this is a problem, because if the advertising does not run, the game level does not load, what can I do?