title: FCM background sync failed: AUTHENTICATION_FAILED
body: <p>I tried to get real time notification on Android using FCM. When I try running my app using emulator, notification message appear correctly. but when I try it on real device (xiaomi redmi note 3), the notification doesn't appear. The token always return null, and I get this error:</p>
  
  <pre><code>FCM background sync failed: AUTHENTICATION_FAILED
  </code></pre>
  
  <p>I've been to try read all same problem, there are 2 reasons why the problem appears:</p>
  
  <ol>
  <li>Device not have Google Play Services</li>
  <li>No internet connection</li>
  </ol>
  
  <p>but I'm sure that my device have Google Play Services and is connected to internet, but the problem still exists.</p>
  
  <p>How can I solve this problem? Any suggestion would be appreciated.</p>