In order, because the first one solves most of these:
1. **Make sure you are signed in to Google Play Games (Android) or Apple Game Center (iPhone).** The game signs in at launch, and a sign-in that cannot complete is the usual cause of a launch that never finishes.
2. Check your internet connection is stable, and try switching between Wi-Fi and mobile data.
3. Make sure the game is on its latest version.
4. Close the game completely - off the recent-apps list, not with the home button - and open it again.
5. Restart the phone.
Do not uninstall the game as a first step. Uninstalling removes what was stored on the phone, and if the progress was never synchronised to an account it does not come back.
If it still will not start, report it with your phone model, your Android or iOS version, the game version and your Player ID.
