.... I have Windows 11 and not seeing the above. I work solo, so have just logged it with IT Service Provider. ...
Hi EDYOT:
Are you sure you are having the same problem that was described in Amit Rakibe's original post on page 1 of this thread? Where are the MS Office files located that you are unable to open (e.g., are they stored on the hard drive inside your Win 11 computer on a partition other than C:\ drive)? Do you have a local area network with a central file server (e.g., is your Win 11 computer a client on a client/server network, and are your MS Office files saved on a mapped drive called X:\ or some other letter that is actually located on the server instead of your local computer)? Are your problem MS Office files located on a cloud service like OneDrive, etc.?
See the support article How to Find the Path of a Network Drive in Windows 10 (which I assume is still valid for Windows 11). I'm a "regular" home user and my 250 GB SSD hard drive only has one main partition (C:\ drive), and the only network location I see on my computer is for the memory card reader on my wireless Epson printer. I recently had an issue opening my MS Excel files (saved in my usual C:\Users<myusername>\Documents folder) but that problem was traced back to the Exploit Protection in my Malwarebytes Premium anti-malware - see Ron Duca's 13-Jun-2022 Password Protected Files Will No Longer Open On Desktop Computer.

Dell Inspiron 15 5584 * 64-bit Win 10 Pro v21H2 build 19044.1766 * Firefox v101.0.1 * Microsoft Defender v4.18.2203.5-1.1.19200.6 * Malwarebytes Premium v4.5.10.200-1.0.1702 * MS Office 2019 Home and Business Version 2205 (Build 15225.20204 Click-to-Run)