just finished all spartan ops and no achieve?

why? i hate spartan ops and forced myself to play for an acheivement and it doesnt even unlock -____-

which one?

the achievement for beating first 5 spartan ops episodes

then just replay the 1st mission on episode 1 on easy, it should pop up

This happened to me earlier, I thought it was because I played some on easy so I went back and played one chapter and the achievement unlocked. Try just playing a random level, it worked for me.

Yup happened to me too. I even completed all of them on legendary.