Reinstalling or restarting the game is a good practice and often enough will solve most technical problems that you might encounter.
To RESTART the game just make sure to exit the app and immediately after launch it again.
To REINSTALL the game, make sure you follow the next steps.
- Tap and hold the game's icon until it starts shaking. Tap the X sign next to the icon in order to delete the app.
- Once the app was uninstalled, go to the App Store and download the app once again.