If it isnt visible when you go here, try closing outlook and reopening it. See if it appears.
If you are using the "NEW OUTLOOK" there has been issues noted on that platform with Shared Mailboxes, and you can try to add it manually.
The shared mailbox should appear in the new outlook under the shared with me folder after a few minutes. You can expand it to see if this is the case.
If it is still not appearing, you can try to add it with the following steps and check whether the shared mailbox displays in your Folder list under this folder.
right-click on the account name or shared with me folder in the left navigation pane, and then choose Add shared folder or mailbox.
In the Add shared folder or mailbox. dialog box, type the name or email address of the shared mailbox, and then click Add.
