Pip concerns for attending assesment

Im not really sure were to start..my son has phycosis and anxiety he has been sectioned on more than one occasion..for the last 2 years he has had alot of support from his cpn he was a great help and it took alot of my worry away..he has got better as hes had the support there but still has difficulties..he is on medication quitiephine and pregablin..just over a month ago his cpn retired and he has a new one..now here is were i have the worry..he does not know he new cpn well nor does she know him as well as his old cpn did..he had to go for a new assesment for his care plan and has been getting assesed for his daily living needs..his sister took him for his appointment last week as i was ill myself..he wanted to go in alone..he told his new cpn he did not want to talk..now she has said she will discharge him in 6 months as he is not engageing..of all the times for this to happen ..he has just received a letter for his pip review consultation..he has never had to have a face to face..his old cpn would give him a good covering letter to avoid him anymore worry and distress..im very worried as he is not only going to loose his cpn but looks like his benefits aswell..great stuff i can see were this will all lead..i am so sorry this is long but i dont know how to help my son more strain for me too now..i dont think i will get him to the consultation as he can be very difficult when he has to see new people or go to new places..all his cpn can say is her hands are tied because he woant engage..can anybody advise what i can do to help him
Thankyou