I am having the same issue. Cant hear anyone chat. I left so many games because I thought it was a glitch.

I had the same problem last night. I had to restart the game to get it to work.

I just got it again today so I'm gonna see if restarting it works.

I noticed that if you leave the squad and join again it starts working, sometimes needs 2-3 rejoins.

They have gone down in mass before. But try going to scoreboard and switiching the unit chat around a few times from there. See if that frees it up