Google has changed the SDK.
You need to extend the ComponentDiscoveryService by adding DatabaseRegistrar.
Add this to the end of your manifest (manifesteditor)
AddApplicationText(
<service android:name="com.google.firebase.components.ComponentDiscoveryService" >
<meta-data
android:name="com.google.firebase.components:com.google.firebase.analytics.connector.internal.AnalyticsConnectorRegistrar"
android:value="com.google.firebase.components.ComponentRegistrar" />
<meta-data
android:name="com.google.firebase.components:com.google.firebase.iid.Registrar"
android:value="com.google.firebase.components.ComponentRegistrar" />
<meta-data
android:name="com.google.firebase.components:com.google.firebase.auth.FirebaseAuthRegistrar"
android:value="com.google.firebase.components.ComponentRegistrar" />
<meta-data
android:name="com.google.firebase.components:com.google.firebase.database.DatabaseRegistrar"
android:value="com.google.firebase.components.ComponentRegistrar"/>
</service>
)