Wasn't sure if I was doing something wrong or if some of the achievements currently have problems. I was playing some Halo: Reach recently as it had been a few months and I figured I would do some housekeeping on the achievement side of the game. I started my solo legendary run (ffffffuuuuuuuuuu) and also jumped into the multiplayer again. Specifically three of the achievements are being a pain in the ass and not popping:

License to Kill

From Hell's Heart

Emergency Room

Wasn't sure if any Bombers could give me some tips as to what I might be doing wrong or if there really is a bug with these. I am playing in matchmade games.

You have the DLC I'm assuming?

Well I assume you have the Halo Anniversary DLC maps otherwise that's your problem right there.

Yes, I have all of the DLC

I think you need to do them in their respective DLC maps.

What I've found elsewhere online would suggest that you have to fulfil the achievement requirements on the Anniversary maps, or you won't unlock them.

Weird ive gotten the dlc stuff outside of the respective dlc maps. Ill try that. Thanks

Not really sure. Almost completed a solo legendary run on the single player...that in and of itself will finish all of the original set of achievements for me in the game. Still would like to get the others if I can, but with how some of the playlists are setup I am not sure if that's going to happen or not. Oh well, we'll see...not a big deal in the end, especially as Halo 4 is out on Tue.