For me seems like intentionally M$ broken the old office license check (2019 on MacOS) and it stopped working (it works but asks to Activate license and refuse to save files – how clever). No recent upgrades of MacOS, no changes at all lately to anything on this machine.

Then I tried to reactivate it , reinstall it, whatever… finally reached M$ $upPOORt which said it is normal and I should buy newer version ?!?!?

The question was: buy or to say bye bye to M$ office?

And the decision…

One more Mac without M$ $H&^*ty OFFICE.

The working ALTERNATIVES: I installed on the Mac thepacel ONLYOFFICE http://onlyoffice.com/download-desktop and later when available will use also https://office.eu/