If you restore an Office 365 Shared Mailbox via the Microsoft 365 Admin Center > Users > Deleted Users, it will restore the associated user account in Blocked state with ExRemoved… address, but the Shared Mailbox itself will still be nowhere to be found.

The proper way to restore deleted Shared Mailbox is via PowerShell:

Undo-SoftDeletedMailbox -SoftDeletedObject shared-mailbox@email-address.com

October 2023
Microsoft Office 365
Microsoft Admin Center
PowerShell