When users in an Exchange hybrid deployment try to open the calendar for a room mailbox in Microsoft Outlook, they receive one of the following error messages:
could not be updated.
Cannot display the folder properties. The folder may have been deleted or the server where the folder is stored may be unavailable. You don't have appropriate permission to perform this operation.
This problem occurs if the room mailbox was created by using the Exchange admin center in Office 365 or Exchange Online PowerShell, and if the room mailbox doesn't have an associated Active Directory account in the on-premises environment.
To resolve this problem, use SMTP matching to link the room mailbox in Exchange Online with an on-premises account. For more information about how to do this, see the following Microsoft Knowledge Base article:
2641663 How to use SMTP matching to match on-premises user accounts to Office 365 user accounts for directory synchronization