Installing Microsoft on MacBook with older operating system

Are you using macOS Catalina 10.15.7??

If your OS is above version 12 but below 14, your office products can be functional, but Microsoft no longer maintains or updates that version. In this scenario, you can install the older downgraded version.

However, if your macOS is below 12, which is your scenario, Office products will now enter reduced functionality mode. In other words, the OS is too old to receive the licensing update the Office now requires. Unlike the first scenario, installing an older version will NOT work for macOS under 12.

This is an update that occured on July 13th and Microsoft shared it here: https://support.microsoft.com/office/update-microsoft-365-or-office-on-your-macos-or-ios-device-f418ae5d-bb5f-4078-b3d9-9340f5dd084e?apid=ets

If your device cannot update its OS to at least 12, your options will be: Use the web version or an alternative like LibreOffice. And you want to cancel your subscriptions.

Install Microsoft 365 version 16.88, the final Office build compatible with macOS Catalina 10.15.7, instead of the current installer that requires a newer macOS version.