Actually I got the admob banner working, for the full screen interstitial banner there is a bug for refresh fullscreen in CocoonJS plugin that Ashley will fix in next build. Already report it to Ashley.
My game is using CocoonJS with banner and interstitial ads and clay.io plugins.
My first game using Construct 2 engine. <img src="smileys/smiley17.gif" border="0" align="middle" />
The banner might not show immediately or even not showing at all.
Maybe backup original file and try using the latest beta ?