Are you running Duplicati as a service under the special LocalSystem user context?
Duplicati defaults to storing its configuration in the user profile. For LocalSystem this is C:\Windows\System32\config\systemprofile\AppData\Local\Duplicati. This area is unfortunately affected by major Windows 10 updates (like upgrading from 20H2 to 21H1), and presumably when you upgrade from Windows 10 to Windows 11.
After an upgrade you can find the Duplicati files in C:\Windows.old. You could copy them back to the new C:\Windows folder, but the better option is to not store those files there at all.
(In my opinion Duplicati should store the data in C:\ProgramData when it’s being run as LocalSystem.)
There are many previous threads on this topic, which you can peruse for more info. Here are a couple: