Resolution:  

1)  Search Outlook (new) in the search bar and click it.

2)  Under the section on the left-hand side that contains your email address, find "Shared with me" and right click it.

3)  Select "Add shared folder or mailbox", type the name of the mailbox in the box and click add.

***If you're unable to add the shared mailbox, please ensure that you have been granted access to it by the mailbox manager.***

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