Yes, you can board. DO NOT cancel that passenger that is having an issue. There is no rule that everyone must board together. Get there when you get there and board. The missing passenger will eventually be a no show. If you cancel that passenger, you will have an issue. EDITED - just realized it was CAS. I did not catch that, sorry. Best you can do is to call CAS and ask, but I don't think they will let you board. 😞