If you receive the message that you cannot edit Office files, you can try to solve the problem with the following steps.
1. Start all Office applications installed on your Mac, click on the name of the application in the menu (e.g. Word) and select "Sign out". Then close the application.
2. In the Finder, click on "Go to" and then "Go to folder".
3. Enter the following in the field: ~/Library
4. Click on the Group Containers folder
5. Locate the following three files/folders and drag them to the Trash
UBF8T346G9.OfficeOsfWebHost
6. Empty the recycle bin and start an Office application to check whether you can now edit the documents.
7. Restart an Office application, log in again and try to edit the file again.