This usually occurs when the user has the Deleted Items Registry Edit enabled to store deleted items in the delegate’s Deleted Items Folder. The user will need to ask the person who shared the calendar with them to grant them at least “Author” permissions to the mailbox’s Deleted Items Folder.

Instructions

The person who shared the calendar can do this in Outlook:

1. Right-click their Deleted Items folder and select Properties.
2. Then click on the Permissions tab and click Add.
3. Enter your name to find yourself in the Address book, double-click on your entry and click OK.
4. Then beside Permission Level select Author or higher.
5. Then press Apply and then OK.

The person who shared the calendar can also do it in Outlook Web Access (OWA):

1. Right-click their Deleted Items folder and select Properties.
2. Click the + icon.
3. Enter your email address and click Add.
4. Then beside Permission Level select Author or higher.
5. Then press OK.

If the shared calendar is a resource calendar, the Office 365 Support Team should be able to grant the user permissions to the resource’s Deleted Items folder using their Admin accounts.