Why did admob ads stop showing in the game?

Question

Android

Admob ads stopped showing in my android game made on Unity.
I added ads using a plugin from google.
For several days everything worked fine and then the ads stopped working, while I did not change anything in either the game or the admob settings.
New ad requests are coming in, but the ad isn't showing.
Note. For April 15, 59 requests and 0 impressions