For Android:
- Go to the "Settings" menu on your device.
- Tap "Storage".
- Tap "Internal Storage" under Device Storage.
- Tap "Cached data"
- Tap "OK" when a dialog box appears asking if you're sure you want to clear all app cache.
NOTE: Clearing app cache will not delete app data like account information. App data, like account information, can be deleted from the same menu - proceed with caution if you decide to do so.
Deleting and reinstalling the game may help as well. To restore an account linked to a social network (Facebook, Google Play Games) please finish the tutorial, go to the settings menu screen and initiate the link process again. Choose your old account on the next screen.