AndroidManifest.xml

Configuration

Application configuration (Activities)

Inside the application section you must add the following (if you don't have it already):

<!-- AdActivity from Google Play Services, needed by Tappx -->
   <activity
    android:name="com.google.android.gms.ads.AdActivity"
    android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"
    android:theme="@android:style/Theme.Translucent" />
<meta-data
    android:name="com.google.android.gms.version"
    android:value="@integer/google_play_services_version" />