Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
There are many problems reported with the Office apps on an Apple Mac device after the July update, Microsoft indicate updating the apps should resolve the problem, however most people indicate that does not resolve the problem.
The best option is to completely uninstall the Office apps using the steps on the link below, then download and reinstall Office from your Microsoft account online.
https://support.microsoft.com/en-us/office/lifecycle/officeinstall/uninstall-office-for-mac