When a user tries to accept the meeting invitation from the Inbox of the shared mailbox in Microsoft Outlook, they receive an error message that resembles the following:
Cannot open the Calendar folder for user "room alias". The operation failed.
The user is able to accept the meeting request from the Inbox of the shared mailbox in Outlook on the web. However, the user who sent the meeting request doesn't receive an email message that confirms that the meeting was accepted.
This behavior is by design. Users who have access to the shared mailbox don't inherit permissions to the calendar of the room mailbox.
Users who have full access permission to the shared mailbox must have explicit editing permissions to the calendar of the room mailbox. To assign editing permission to users for the calendar of the room mailbox, follow these steps:
Do one of the following, as appropriate for your situation: