I have the exact same issue. I've been pulling my hair out trying to figure it out. I've researched so much and the only thing I've been able to see is the following information.
While in a party, your squad chat has been disabled. This is part of the game.
I've seen pictures where people have an option in the audio menu where you can turn on Squad or party chat. I am on PC, and I don't see that option whatsoever.
I'm going to make this situation more interesting. I have a buddy that I play with, so I like to invite him in a party. But as soon as we bring in random players to fill a four-man team, I can only hear my buddy in my party, and I can't hear the rest of the squad. The weird thing is he can still hear the other random players, but I cannot. I always host. Then when I play by myself, I can hear whoever has a mic in the squad. When I'm in a party, hot mics will come up as yellow. When I'm in a squad without my buddy, hot mics come up as green. Have you been able to find a resolution to this? Any help would be greatly appreciated. Thanks.
I am on PC and have been having the exact same issue as you described except I have the option to toggle between squad and party. In party, I can hear my party members and not anyone in the squad (expected). If I change it to squad, I cannot hear or talk to anyone. People in my party can hear the other squad members. They are on xbox if that matters, but it shouldn't.
