If your app is not working or experiencing an issue it can due to your user no longer being valid. To fix this please do the following:
1 - Logout and log back in.
2 - Close the app from your recent apps (double tap home button / swipe up to see recent open apps) and re-launch it.
3 - Please update the app to make sure you are on the latest version, see here how to update your mobile device > https://support.apple.com/en-gb/HT202180
4 - Make sure you are logged into the same account you made the purchase under, this would be where you received your email confirmation.
If you still experiencing any issues please submit a support ticket and let us know your phone and OS version.