You can add contacts to case teams, but they can only access cases when they’re enabled as customer portal users assigned to case page layouts.
Visible In Customer Portal
If you want members in the role visible to customer portal users viewing cases, choose Visible in Customer Portal. Even if Visible in Customer Portal isn’t chosen, customer portal users added to case teams can view themselves on Case Team related lists.
Case Team access for Contacts applies specifically to ‘Customer Portal Users’ which are associated with a unique, legacy license type. ‘Customer Community’ Users and ‘Customer Portal’ Users, while similar, are not the same.
Vote for this idea for Customer Community licenses – https://trailblazer.salesforce.com/ideaView?id=08730000000DlPpAAK.
Customer Portal user = Customer community License ?
No. They are not the same.
I have a contact and it has a community user enabled of type "customer community License". Now on Case teams, I added this Contact. Now If I try to login to that user in community, I have observed the Case record is not shared. why so ? if this is Working as designed then what's the point of assigning Contact on Case team ?
Case Team access for Contacts applies specifically to 'Customer Portal Users' which are associated with a unique, legacy license type. 'Customer Community' Users and 'Customer Portal' Users, while similar, are not the same.
Vote for this idea for Customer Community licenses – https://trailblazer.salesforce.com/ideaView?id=08730000000DlPpAAK.