On macOS Monterey 12.7.6, Microsoft 365 apps are supported only up to Office for Mac version 16.88/16.88.1 (and, per later guidance, 16.89 dated September 10, 2024). Newer builds require macOS Sonoma or later and will not install.

To get Microsoft 365 working on macOS 12.7.6:

1. Make sure there is a valid Microsoft 365 or Office 2021/2024 license associated with the account. A current license is required to activate the older build.
2. Download an older Office for Mac build that supports Monterey (for example, 16.88 or 16.89) from the Office for Mac update history page listed in the context:
   • Use the long table of downloadable versions on the update history page to select version 16.88 (or 16.89) for Office for Mac.
3. Install the downloaded package on macOS Monterey 12.7.6.
4. After installation, open any Office app and sign in with the licensed Microsoft account to activate.
5. Run Help > Check for Updates once to move to the final supported build for Monterey (for example, 16.88.1 for Outlook and PowerPoint). AutoUpdate does not need to remain enabled because there will be no further updates for Monterey beyond that version.

If upgrading macOS to Sonoma or later becomes possible, newer Microsoft 365 builds can then be installed and updated normally.

References:

• Upgrade macOS to continue receiving Microsoft 365 and Office for Mac updates
• Download, install, or reinstall Microsoft 365 or Office 2024 on a PC or Mac
• Download volume licensing products
• Deployment options for admins for Office for Mac
• Troubleshoot installing Office
• Office 365 won't install - Microsoft Q&A
• Cannot install Microsoft 365 because my os is too old - Microsoft Q&A
• where can i find an old version of Office 365 for mac - Microsoft Q&A
• Help! I can't get 365 to work. Can I use it on my MacOS or do I need Office? - Microsoft Q&A
• Office running on OS 12.7.6 - Microsoft Q&A