In Microsoft Office 365 dedicated, calendar items are visible when you open a shared calendar in Microsoft Outlook Web App (OWA). However, these calendar items are not visible for the shared calendar when you perform the following actions:
You use Microsoft Office Outlook to view Free/Busy data for the shared calendar.
You use Outlook to open the shared calendar.
Note You have limited Free/Busy permissions for the shared calendar.
This behavior is by design. When the Read permissions level for the shared calendar is set to Free/Busy time or Free/Busy time, subject, location, Outlook does not display an item that is marked as Free. For example, the screen shot for this item resembles the following:
To resolve this issue, set the Read permissions for the shared calendar to Full Details. For an example of Read permissions information, see the information in the following screen shot: