Why can’t my son hear his PlayStation friends in group chat?

We’ve been having this trouble ever since I made his account. I’m not very savvy when it comes to Xbox or call of duty so I’m needing help pretty please. I have his account set to as a kid, but I don’t see why that would make him not be able to hear his friends in chat. He can hear his Xbox friends, but no one that has a PlayStation. Can anyone give me advice on what to do to fix this?