Saouls

Hello, I have a little problem, I have a haunter lvl 78 and he won't evolve. I tried everything: firstly exchanged him with a friend when he was lvl 76 5 times but nothing happened (his haunter evolved but not mine) later I tried again with someone else, and again he won't evolving. He don't have an everstone or something else, I hope it's just a bug, help me pleas Saouls