cannot open 2021 Office installed with old email address, MacBookPro, 2023

For Office 2021 on Mac, the installed apps must be activated with the Microsoft account that the product key was originally redeemed to. If Office was installed with an old email address, use this path:

1. Check whether the Office 2021 purchase is available under the Microsoft account dashboard Services & subscriptions.
2. If it is listed there, close all Office apps and reinstall Office from that account instead of using App Store versions or an old installer.
3. If the apps were installed from the Mac App Store, remove them and reinstall the Microsoft installer version. App Store installs can require different licensing behavior.
4. To remove and reinstall on Mac:
   • Close Word, Excel, PowerPoint, and Outlook.
   • Open Finder > Applications.
   • Move the Office apps to Trash.
   • Download the correct Office for Mac installer package.
   • Open the package and complete installation.
5. After installation, open Word from Launchpad and start activation.
6. If Office shows Unknown Error 0x0 or License Not Found, first make sure macOS is version 12 or later, then update Office using Finder > Applications > Microsoft AutoUpdate > Update All.

If the old email account was the one originally used to redeem the product key and that account is no longer accessible, the key normally remains linked to that original Microsoft account. In that case, Microsoft Support is the path to verify the purchase and help recover access to the license.

References:

• Download and install or reinstall Office 2021, Office 2019, or Office 2016
• Microsoft Office activation and the Mac App Store
• Unknown Error 0x0 or License not found error in Microsoft 365 or Office running on macOS
• Cannot access Office 2021 installed March, 2024. Email server for that account has shut down. I have opened a new account. Is there a way I can access the Office product? I have the product key. - Microsoft Q&A