title: Can't write to Firebase database
body: <p>I can't write to Firebase. I use exactly as in the tutorial but it's not working.</p>
  
  <pre><code>    @Override
  protected void onCreate (Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.welcome);
  
  FirebaseDatabase database = FirebaseDatabase.getInstance();
  DatabaseReference myRef = database.getReference();
  myRef.setValue("aaa");
  ...
  </code></pre>
  
  <p>Also I have changed the rules to:</p>
  
  <pre><code>{
  "rules": {
  ".read": "true",
  ".write": "true"
     }
  }
  </code></pre>
  
  <p>Also my google-services.json is just downloaded from the project.</p>