Hi Tomasz,
Thank you for getting back. You’re absolutely correct, in my haste (too much rushing :-), I did indeed forget to give Publii the permission to access files on the Documents folder.
So all it took was to complete the first 4 steps from the helpful reference link you provided: https://nektony.com/duplicate-finder-free/folders-permission and click the check box to allow permissions for Publii. Seconds later, of course Publii starts normally again. Thank you again.