The game doesnt give you the achivments?

Since i have been playing halo tmcc i discovered that the game doesnt give you some achivments like the pillar of autumn. I made that achivment and the game just says to me Done! Unlocking… But the game doesnt give me the achivment so 343 help us. Me and the comunity we need help with this achivment bug. If you can help me 343 with this my gamertag is: Assassin117 lol Please help us 343 the comunity needs your help.

If 343 is reading this you have done a great work but i have a problem. I have done some achivments but i made the Pillar of Autumn and the game doesnt give me the achivment. I have the achivment but the game doesnt give it to me if you can send me an update or a solution to my profile please my gamertag is: Assassin117 lol