• You have reinstalled the game and the in-game images and cache are still getting downloaded onto your device.
  
• Your internet connection is unstable.
  
• Your game is not updated to the latest version.

In order to fix this we recommend trying the following:

• Try closing all background apps, and restart the game.
  
• If it doesn't help, please try reinstalling the game. Make sure you have linked the account to Facebook/Google Play/Game Center before reinstalling.