If your app is stuck spinning on Android and you can't even see a login screen, you will need to force stop the app, clear the app's data, and clear the app's cache.

On most Android devices this can be done by:

  1. Go to your device's Settings
  2. Navigate to the Apps or Applications section
  3. Tap Force Close
  4. Tap Clear Cache
  5. Tap Clear Data

Now, open the app again and it should load!