completed halo 4 on normal no achivements?

Games Other Halo
1

just completed halo 4 on normal difficulty and didnt ever get the achievement for it, do i have to do it in one sitting or something?

2

sorry, i wouldn’t know. i started campaign on legendary.

3

i completed it on normal my first time around and i got the completion achievement.

only advice i have is to play it again on a harder difficulty