When a user with snc_external role navigates to Service Portal, they get the error "Security constraint prevent access to requested page".
One of the reasons this could happen is if the $sp page is set to non-public in Public Pages [sys_public] table.
This means that the Active checkbox on $sp is unchecked in sys_public table.
- Navigate to sys_public.list in the filter navigator.
- Look for Page: $sp
- Make Active = true