You may need to change the identity that you are using for Microsoft 365 if the way you pay for your license changes - eg from a personal to a business license.
To change identity:
- Sign out of Microsoft 365 (you can follow this guide.)
- Quit all Microsoft Office applications that are running. If you're not sure which are running you you can re-start your computer.
- Start a Microsoft Office application (eg Word) and sign in with the identity you want to use. When you start Word, you will be asked to sign in. If you miss this sign-in opportunity you can also sign by clicking the Activate button that will be visible towards the top of the screen as follows:
If you are not signed into Microsoft 365 then you will not be able to edit documents in Word, Excel, PowerPoint and so on.