Boyfriends ex is being childish

So me and my boyfriend broke up for about 2 months and while we were broken up he got with another girl. He took a PS4 over to watch movies on and when they broke up he forgot to get it on the way out. We’re back together now and I think she found out about it and is completely ignoring everything he says to her. She opens his messages and doesn’t reply and doesn’t answer either of our phone calls. A ps4 isn’t cheap. I dont know what to do. He’s already tried just showing up at her house but it didn’t work. She’s caused so many fights in our relationship over him not getting it sooner but now that he wants to get it she’s being childish.