I have been playing Halo: Reach for a while now and i have been the last man standing several times on 'Infection', there is also an achievement for doing this, and yet it is still locked. Aswell as the achievement 'Emergency Room' I have downloaded all DLC for the game, including the 'Anniversary Pack' wich the achievements come under. It seems all other achivements so far are working fine just these two. I have even tried deleting and re dowloading the 'Anniversary Pack' but this didn't work as I guessed.
Some help with how to fix this would be much appreaciated, Thank You!