So i got on today to play some Halo 5, i noticed that everyone is muted in my lobbies and that i cant unmute them, has anyone else had this problem and does it have a fix ?
either your NAT type doesn’t allow for you to hear them or you muted them all by accident and a glitch is preventing you from unmuting them. NAT type if fixable and the glitch, well you’ll never know when it’ll pop up so you either deal with it for the match or… deal with it for the match, you have no choice in the matter for that one 
Go to your settings, go to network, and find out what your nat is.
This also use to be how past games looked if you were prohibited from talking in the game. I have no idea what it looks like anymore as I have not heard of that punishment going out for ages.
i tried CoD Black ops 3 but it didnt do it on there, i can still talk to people in other games