ok, so I had this problem too. I have tried EVERYTHING I read to fix it and nothing worked. So I just played and had one of my teammates that could hear me in discord translate for me. I fixed the issue and it was so simple, the Devs should have found this way sooner.
My problem: My crew could hear me in game, I could hear most of them in game, but I could not hear proximity chat, and others outside of my crew could not hear me at all.
I play on PC and Xbox one (no problems on X1). My PC uses a USB mic/headset and I play with a Xbox 360 wired USB gamepad.
The FIX: My USB headset is wireless and it died, so I grabbed the old Xbox360 headset and plugged it into the gamepad.... BAM!!! I hear EVERYTHING!
So just to confirm that this is where the problem is, I unplugged my Xbox gamepad and started the game again with my headset on. Guess what? BAM... It was working. if you have this problem too, check to see if you have a headset port on your controller. I would say it is safe to assume that it has some priority over proximity chat that overrides our settings. The proximity chat is there, it is just being redirected to the headset port on the controller.
I hope this helps all of the MUTES out there so we can hear the trash talk that comes with the battle!