I bought Halo CE last Saturday and had a lot of fun downloaded the map pack that you get with the game got 10 new achievements to get but they won't unlock so far I should have 3 headshots in a row, be the last surviving member in infection, infect 3 different players in 1 round and pummel an enemy whilst jet-packing but nothing is unlocking I've tried them in different game types I tried Anniversary game type I've tried them on different maps all sorts but nothing is working anyone have any suggestions to make anything would be helpful