Android AdMob Advertisement Testing
At the time of writing about testing Android AdMob, the ad unit id for testing is BANNER is :ca-app-pub-3940256099942544/6300978111
So check that this is the current ad unit id before using this code.
Always test with test your Android Application When building and testing your apps, make sure you use test ads rather than live, production ads. Failure to do so can lead to suspension of your account.
Note: If you haven’t created an AdMob account and registered an app yet, now’s a great time to do so. If you’re just looking to experiment with the SDK in a Hello World app, though, you can use this App ID to initialize the SDK: ca-app-pub-3940256099942544~3347511713
One you have updated your code, you should then see something like the following example Android AdMob appear on your screen, for the banner example:
Other sample Ad Units can be found at: Android Sample Test Ad unit id’s