See if the secondary calendar is a sub-folder of the primary 'Calendar'.If the secondary calendar was created using Outlook on the web, then skip to the grant permissions section.Verify if the secondary calendar is a sub-calendar of the primary 'Calendar': Important: Microsoft is aware of this issue and is working with Apple to find a better workflow than requiring the owner of the calendar to have to use an Outlook desktop client to set the permissions. In this document, you will learn how to share a secondary calendar (not the primary 'Calendar') so that a user who is using Outlook 2016/2011 for Mac can open/subscribe to it. You have been granted permissions to a secondary calendar and the permissions are not set correctly.
Ask the owner of the calendar to grant you the appropriate permissions.
Any permission below this level will cause this error and the calendar will not be opened. There are a couple of reasons why this error can occur:
When you attempt to open or subscribe to a another user's calendar via Outlook 2016/2011 for the Mac, you receive the error below:
