A number of people have mentioned the same problem but I've opened a new thread as my issue is intermittent.
I have a macbook pro
And an Office 365 Subscription
Siince I upgraded to Big Sur I have an intermittent and random problem when starting the various different Office 365 components
This is for Word but ALL apps suffer the same problem but sometimes they ALL start without issue. Sometimes responding Ignore and OK to the above error boxes means the app starts. Sometimes it takes a second attempt (never more than 2 attempts).
I've reinstalled Big Sur from scratch (and MS Apps) and I've just updated to 11.2 but the problem still exists.
Others have this problem but it seems to be more usual for the apps not to work at all. A lot of the responses concentrate on permissions but snce the apps sometime start without issue I dont see how that can be the problem.