Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
An update turned out to have an undesired side-effect; see https://support.microsoft.com/en-us/servicing/os/microsoft-365/kb5002907-optional-update-for-out-of-date-microsoft-365-apps-installations. The fix is to reinstall and reactivate your version of Office. In most cases, you can reinstall from your associated account. If you run into activation issues, see https://support.microsoft.com/en-us/windows/activation/activate-microsoft-perpetual-products-using-the-product-activation-portal .