Answer : There are a few things you can do to try to fix this. First, make sure you're using the latest version of the app. You can check by going to the App Store or Google Play and checking your app's current version number. If you're not using the latest version, download the latest update and try again.
If that doesn't work, try restarting your device. Sometimes all it takes is a quick restart to clear up any glitches. If that still doesn't help, delete and reinstall the app. This will erase all your progress in the game, but it might be worth it if nothing else has worked so far.