title: Firebase Cloud Messaging tokens stop working - 404 NOT FOUND
body: <p>We have a problem where Firebase Cloud Messaging tokens seem to have stopped working.  We register with Firebase when the application first starts-up and then we call an API to store the token on our server.</p>
  
  <p>We upgraded the app last night and checked that a sample of devices successfully registered themselves and that we could send messages.</p>
  
  <p>Today, however, some calls to Firebase from our server are returning:</p>
  
  <pre><code>{
    "error": {
      "code": 404,
      "message": "Requested entity was not found.",
      "status": "NOT_FOUND",
      "details": [
        {
          "@type": "type.googleapis.com/google.firebase.fcm.v1.FcmError",
          "errorCode": "UNREGISTERED"
        }
      ]
    }
  }
  </code></pre>
  
  <p>These calls are using the same tokens as last night.  Half are working and half not.</p>
  
  <p>We don't have any code that explicitly unregisters our app.  What else might have caused this issue?</p>
  
  <p>The app is written in C#/Xamarin and we're using <a href="https://github.com/CrossGeeks/FirebasePushNotificationPlugin" rel="nofollow noreferrer">CrossGeek's plugin for Firebase</a>.</p>
  
  <p>Thanks,</p>
  
  <p>J.</p>