A family of Microsoft word processing software products for creating web, email, and print documents.
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, 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. Installing an older version will not work for this scenario.
This is an update that occurred 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.