Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
There are a couple of widely reported problems with the Office apps on an Apple Mac at the moment due to the July 13 update.
If you are unable to upgrade your MacOS version, the last version of Office that will work on MacOS Monterey is 16.88, that is available on the long table on this link to all the downloadable versions from the Microsoft servers.
https://learn.microsoft.com/en-us/officeupdates/update-history-office-for-mac