Ok can someone please help explain to me how the hell to get the voice chat to work?????? in multiplayer or coop

I have it turned on in the uplay settings, when you hit shift and F2 at the same time, i tryed it on all the settings, continuous transmission, than holding alt in game, nothing happens, than tryed making them both the same button for the uplay settings and the in game settings, still nothing.

But i have read some fourms with people saying they have gotten it to work, so i would really like to get this to work, even if people cant talk back, especially in multiplayer be nice to let the guy running up the tower that theirs a guy right behind him.

Any help at all is very much appreciated, preferable a quick response would be nice but, i would really be happy with any response lol.