Q. After introduction new cat is friendly but when he tries to play w/ old cats they avoid/attack. Tried catnip, treats, scent swabbing & play sessions.
A. Introducing a new cat takes time. I am not sure how long it has been since his arrival but I find old cats can be pretty stuck in their ways and sometimes a bit snobby. It can take longer for them to get used to the idea of another cat, and even longer to decide they are okay with it. Sounds like you are doing everything right from your side of things, but keep it up. It will help.