Hi Tong2013,
Sorry for the delayed response.
From your description, I understand that you cannot make appointments in the room calendar in Mac operation system, but you can do this before. Also you can make appointments in this room calendar in Outlook in Windows operation system. Does the issue still exist now?
Based on the current situation, I would like to collect the following information:
1. Have you received any emails about Office 365 service upgrade?
2. If all the Mac users encounter the same issue.
I recommend you create a new room mailbox to check if the Mac user can make appointments as normal.
Thanks,
Anna Shi
