I'm getting mad here while trying to fix a issue with iCal and Exchange.
After removing and adding back the Exchange Account in 'Setting' 'Internet accounts' the Exchange Group in the calendar has disappeared
Mail and contacts are working fine and are in sync with exchange, but in iCal there is the exchange account missing :-(
I tried several stuff: removed and added the exchange account. Double and tripple checked that "Calendar' is activated in 'Internet Accounts' and that in the Calendar Settings the Exchange account is activated, too.
Then I have stopped iCal, removed everything from ~/Library/Calendars, gone into ~/Library/Preferences and removed everything containing iCal. rebooted several times (as suggested here https://discussions.apple.com/thread/7837872) .
And talked with Apple Care too but the girls were overwhelmed and couldn't help.
The same account works with calendar on my iPhone w/o any problem.
Any help is welcome, I don't want to switch to Outlook just because of this :-(
My system: MBP Retina 13'' early 2015 MacOS Sierra (10.12.2) Calendar 9.0 (2155.15)