If you are using Next-Gen Check-in and have any of your kiosks configured for registration mode you will need to edit those kiosks and enable the two new settings: "Allow Adding Families" and "Allow Editing Families".
These two settings control the ability to add new families on a kiosk and to edit existing families on a kiosk. This means you can configure some kiosks that are more public to only allow adding new families but not edit (and see the details of) existing families.
These new settings only apply to Next-Gen Check-in. The old setting is still used by legacy check-in.