Since August 1, Google Play Store doesn't accept apps that use the old AdMob API, making the upgrade to the new advertising API from Google Play Services compulsory.

An update for RAD Studio XE6 is available (for registered users of one of the XE6 products) at  cc.embarcadero.com/item/29911 . Download and install it, and you are ready to go.

The update offers a version of the TBannerAd component that hooks to the new Google Play Services. You can keep using the same banner ID, so this means that you have nothing to do on your source code to migrate your applications to the new advertising API.

All good? Not exactly. If you run the app... it will simply crash. The reason is that you need to change the manifest file to indicate you want to use this new API, and you'll have to include lines like the following: 

      <meta-data 
      android
      :
      name
      ="com.google.android.gms.version"
      android
      :
      value
      ="4323000"/>
      <activity 
      android
      :
      name
      ="com.google.android.gms.ads.AdActivity" 
  android
      :
      configChanges
      ="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"/>
      

A sample manifest file is included in the download. If you have an existing application, you'll have to update the manifest adding the "meta-data" line and replacing the secondary activity with the "gsm.ads" version. For a new application or if you never edited the manifest manually, just use the one included with the update.

By default, in fact, the manifest you get from the IDE doesn't support features like push notifications or advertising, which require extra line. Notice that the current documentation at docwiki.embarcadero.com/RADStudio/XE6/en/Adding_Advertising_to_Your_Mobile_Apps still lists the older manifest entries.