Hello,DoubtingRich
Welcome to the Microsoft community!
I have realized that your issues.
Is your current Windows login the same account that you are currently experiencing problems with?
Currently your situation is related to the cached credentials of your current local Windows logon account.
I would suggest you try the following as a last resort before reinstalling your system.
1.Search for Credential Manager in the search box in the lower left corner of the taskbar, then find Manage Windows Credentials - find your Microsoft account and select Delete Credentials.
Accessing Credential Manager - Microsoft Support
2.Registry Reset Office
Press Windows + R and type regedit in the Open Run box and press Enter.
Locate the following key and rename the Office folder (right-click it and select Rename (for example, Office will be renamed Officeold)):
HKEY_CURRENT_USER\Software\Microsoft\Office
Then open the word document again to try the effect.
Disclaimer: Registry or workgroup modifications are typically intended for power users, administrators, and IT professionals and can help resolve some issues, but incorrect modification of the registry can lead to serious problems. So, strictly follow the steps below. Make a backup of the registry before modifying it for added protection. For more information about how to back up and restore the registry, see: How to back up and restore the registry in Windows - Microsoft Support
3.New local account: New local account can troubleshoot the problems caused by the system account modifying some personalized settings, the method by switching a system login account to achieve the purpose of restoring the initial settings, you can use this to reduce the interference of some settings on the software. At the same time, you don't have to worry about missing files, all the files installed on your computer are there. The documents that have disappeared from the desktop will be saved in your original account and you will be able to see them when you switch back again.
Manage user accounts in Windows - Microsoft Support
The third method I think has a high probability of working, since it's a brand new login file that's already being used. The only problem is that some of the files on the original desktop and some of the customizations will need to be readjusted, which are in the original account on the C drive USERS.
Feel free to post back if you need further assistance.
Thank you for your understanding and patience and I look forward to hearing from you.
Ryan - MSFT | Microsoft Community Support Specialist