"Generating invalid activity" means that AdMob thinks you were clicking on your own banners / interstitials to increase you CTR (Click Through Rate) and your revenue. If you weren't clicking on your own ads, perhaps some of your friends were repeatedly clicking on them. Keep in mind that a normal CTR goes from 1% to 3% for banners and goes from 5% to 15% for interstitials, so even if you click on a banner once every five ad requests, you will have a 20% CTR which is up to 20 times a normal CTR. If this happens for two or three days in a row, you will be banned from the network. Unfortunately AdMob is very strict in these situations. At this point if you want to use AdMob again, you will have to create a new account with another email address, but you have no way I know of to get your previous earnings. In the new AdMob extension for Stencyl, you will be able to use test ads to avoid this problem.