Hi there! After a deep research, I found the problems.
There a mixture of a problem with r265 of Construct 2, and a compatibility problem between plugins.
These are the steps I followed to make it work again, and make admob and google play services to work fine together:
1) Reverted Construct to r262
2) Installed cocoon-plugin-ads-android-admob version 1.0.12
3) Removed cordova-plugin-play-games-services
4) Installed cocoon-plugin-social-android-googleplaygames version 1.1.5
Cleaned project in cordova cli, removed android and added android again, and now it works :)