This can occur if you've recently changed your SubAssistant account password or if your app's local data cache is corrupt. To resolve this, just log out of the app and sign in again. To log out of the app on Android, open the menu in the app, and then select Logout.  To log out of the app on iOS, go to the Settings section and tap Log Out. Once logged out, tap the Sign In button and then sign in again using your current SubAssistant account user ID (email address) and password.