If your game doesn't start, please try the steps written below according to the device you're using.
- Increase storage memory by uninstalling apps you no longer need. Also, try transferring (or removing) videos and pictures from your device.
- Clear the app cache. To do so on the latest Android OS go to Settings > Apps > select the App > Storage & Memory > Clear cache.
- Go to device Settings > Apps > Google Play Store >Tap on the top right dotted lines and select Uninstall updates.
Read more here: Android Troubleshooting
- Make sure you’re running the latest iOS. To verify: Enter settings > General > Software Update. Here, you’ll see if any updates are available.
- Check your device’s storage capacity. Enter Settings > General > “About” to check available capacity. Free up space by removing unused Apps, pictures and videos. Free up device memory by exiting running unused Apps.
- Exit all apps, and restart your device. This frees up memory.
Read more here: iOS Troubleshooting
In case you weren't able to solve the problem, uninstall and reinstall the game again.
BE CAREFUL: if you have a guest account you need to connect it to Google, Facebook, Apple ID or some other available option, to be able to login into your account again. Otherwise all of your progress will be lost and we won't be able to restore it.