I have an Android application in Google Play and I show a banner at the bottom of the screen.
I uploaded the application three days ago, until now the estimated earnings have increased but today I got up and saw that the banner has been shown 55 times but my estimated earnigs have dramatically decrased to 0.
What is this due to? Is this a sign that I'm doing something wrong and Google is penalizing me?
Well, depends!
How many click did you received today ?
55 impressions aren't enough to make statistics. Check the clicks. It's normal if you have 1-2 click/day that someday maybe nobody click the banner
AdMob pay only for the clicks, not for the impressions.