Problems with Halo 3 Golden Skull Achievements?

[Joseph]

The problem am having is that when I pick up the golden skull, from what I've read, am just supposed to hold it for a while and the "Yay!, you completed an achievement" window should appear, but it doesn't so I thought maybe if I carried it throughout the whole mission something would happen, but it didn't. Am very sure that no one has picked them up before me, so I don't know why this is not working, any of you have an idea?

Thanks
I have try this on Normal, Heroic, and Legendary, plus, I tried it with the first 2 skulls (golden)

 

[pinkempyreal]

What difficulty are you playing on? Try it on Heroic. Also, some of the skulls do not count as achievements. You'll get the option to use the skulls in campaign, but there isn't an available achievement. If there is an achievement for a skull, it will pop up as soon as you pick it up.