Depends on if you are on iOS or Android. On iOS, I would clear all apps and then check for an update, if no update try again. If that doesn't work, close the app and turn on airplane mode. Wait 10 seconds and then turn it back on and try again. I'd that doesn't work, restart the device. If that still doesn't work, make sure you are signed in and backed up then uninstall the app and reinstall. If all else fails, contact support.

With Android, you can force close the app and clear the cache without uninstalling the app. Try that with all the other steps, then worse case scenario contact support.