Ran into this little gem with Excahnge 2016 CU 4 when trying to view the properties of a calendar when the shared calendard's mailbox is configured to have MAPI disabled to disallow client access for the mailbox. This also disables anyone who may have access to update the shared calendar from doing so. To resolve it you must enable MAPI on the user account . at this time I am unsure if this is a bug or by design. I plan to test with CU 5 but if anyone has any insite that would be great.