Hey I was having a similar problem! What dimensions are the layouts in your project?? If you are using a window size that is not compatible with the ad banners, they will not show up. When I was dealing with this problem I alsochanged the name of the 3rd Party Plugin I was having to "Admob Ads". I dont kow if that is important but better to follow Scirra instructions to the dot. I found when I ran a window size(not layout size but window size) of 680, 360 i didn't get any ads AT ALL. It is important to note that I have used the plugin seamlessly before this app I was working on. Anyway after some testing I guessed that maybe the resolution is not supported or the plugin just simply doesn't like other resolutions, even though my app was scaling. So I changed my window size to 1280, 720 or vice versa and the ads worked again =)!!! Check out my Tutorial !!! It will help you get every single step!!
https://www.scirra.com/tutorials/1386/u ... -crosswalk