There is a bug in Due 23.1 and earlier that caused an unintended loss of previously unlocked features. The loss of access is unintended. Features unlocked remains permanently unlocked and there is no change in this policy.
An update (Due 23.2) is now available from the App Store. Please update to the latest version of Due from the App Store to restore access to your unlocked features and/or subscription.
I’m sorry about the inconvenience caused.