Case Owners cannot view their portal cases

As a customer, I can view the case from the portal, but when logged on as the Case Owner, I CANNOT view the case from the portal. The page says "The case could not be found." I would think that this should be enabled OOB. Is this a setting that needs to be configured in Entity Permissions?

ALSO, the Case Owner field is not displaying on the portal case form for some reason, even though I added it to the appropriate form and it has Visible by default checked.