If you've encountered an issue where you opened the app to find either a plain white screen, or a dark patterned screen and were unable to progress to the login, this should help you get the app working again.
1. Open your Settings app
2. Tap "Apps" (alternatively "Apps and Notifications" on newer versions of Android)
3. Open the App info for the Five Good Friends app
4. Open the "Storage" section
5. Tap the 'Clear Data' button and tap OK to confirm
You now should be able to log in to the 5GF app