Does anyone have lotion?
*Raises hand*
Is mayonnaise a lotion?
You mean the main screen in Reach? Like you click on his gamertag, and instead of going to his service record or whatnot, you see the unmute button and it is greyed out, correct? If you are not hearing him but your friends are, that means either you muted him on accident in the xbox menu, not in Reach, or he muted you, same circumstances, probably on accident. Try sending him a message to ask him to check if he muted you.