Shared Calendar

I have a shared calendar for our estimating team.  And used to be able to copy appointments from my "personal calendar" to the Shared Calendar just by drag and drop.  But now it just gives me an error with "unknown reason" pop-ups. It's associated with my email, so I can't send an appt to the shared calendar either. 

Has anyone had this issue and been able to resolve it?  My IT person didn't seem to know what to do either.