Thanks for sharing the details! Because “Save” is not working, do this immediately:
Press Ctrl + A (select all)
Press Ctrl + C (copy)
Open a new Word document
Press Ctrl + V
Try saving the new document
If the new document saves correctly then the original document is corrupted.
Now to troubleshoot the affected file, disable all Word add-ins
Open Word without opening any file
Go to File → Options → Add-ins
At bottom: Manage → COM Add-ins → Go
Uncheck everything
Close and restart Word
Try saving again
If this works then enable add-ins one by one to find the problematic one.
See if this helps. If you need further assistance just let me know.
Best regards,
Kimberly