Halo 3 Famine Skull doesn't activate achievement...?

[Allan]

The difficulty was on legendary and I made several attempts to pick it up but I never got the achievement. I beat the game on normal but not yet legendary so that might be the problem. There is an achievement for the Famine skull so it isn't a silver skull.

 

[Shay H]

Here add me as a friend on your Xbox "XDr DeathX666"
I'll get you the rest of the skulls and help you get achievements so you can get the Samurai sword.
I'll even help you beat the game on Legendary at that.
I'll do it tonight too.

 

[Ryan H]

I don't recall any glitches with the famine skull, but if i were you i would first make sure that i was actually picking up the right skull(hey, it happens to the best of us) or go back and make sure i dont already have the achievement. if it still doesn't work, maybe the skull got glitched with bungie's last auto update, so you should contact them(maybe you'll get recon for discovery