A family of Microsoft word processing software products for creating web, email, and print documents.
If you're not signed in to your account, Microsoft 365 becomes read-only.
Try creating a new user account on your Mac. Then sign into that account and see if you can edit Word files. If you can, it means there is some problem with the user profile on your old user account.
If the problem still exists in the new user account, or if you don't want to switch user accounts, please follow these steps to uninstall: Uninstall Office for Mac Then re-install from the Services & subscriptions page of your Microsoft account.