Problem
None of my scanner appear in the dropdown list in the PaperOffice scan module (ScanConnect)

Test
PaperOffice reads out all available scanners from the same "system scanner file"  as the native Scanner App from the Microsoft Store.

Open Microsoft Store and search for "Scanner"

Install the App and open it.

If you get the message "To get started, connect a scanner.",

it means that your scanner has not been installed correctly.

Solution
Reinstall your scanner original drivers, restart your PC and retry.