Achievement for Lone Wolf Legend on Halo 4

For some reason I completed every level on Legendary on Halo 4 but several achievements haven’t unlocked because it says I haven’t completed the game. It shows up as 7 of 8 missions completed when I look at my achievements under Options and Career but in missions it shows that I have completed every mission in legendary mode. Is anybody else having this issue and is their a way to fix it?