Well all I can say it give it time and make sure he has everything he needs. Cats are very particular creatures, the slightest thing can upset or make them sick – like moving around furniture!they are creatures of habit and do not like having their routine disturbed. It might take some time, up to months before he feels comfortable. Just give him space but don’t ignore him, talk to him as much as you can, and keep an arms length from his nose. let him get used to your sent and keep your small pup away form him for a bit.
I hope this helps please keep is updated!
Best of luck