If you receive an error message saying "Invalid or expired credentials" or "Authentication Needed" when you try to sync, you will need to log out of your Paprika account and log back in. This can be done by going to Paprika's Settings -> Cloud Sync and pressing the Log out button, then logging back in with your correct email address and password.
This usually occurs if you have recently changed the email or password for your Paprika account. For security reasons, we require you to log in again with your new email and password on all devices after either one has been changed. Devices that are still logged in with your old email or password will receive this error message until they are updated with your new credentials.