I have completed all of the spartan ops missions on atleast heroic, and it even says so in the episode selection. However, I went back to look through them as I didn’t get it, and found that all of episode 2 suddenly forgot that I completed all of the missions (atleast once), and yet when I choose the individual missions, it says I’ve finished them on heroic.
Help…?
It’s glitched for everyone.
Oh, so it will be dealt with for everyone soon, right? 
Time will tell.
Play chapter 1 episode 1 beat it and it will unlock. Thats how I got it.
> Play chapter 1 episode 1 beat it and it will unlock. Thats how I got it.
It’s only the second episode that isn’t working for me, not the first.
Was a Red vs Blue easter egg activated in the chapters that weren’t being counted for you? It won’t count toward your achievement if they were.
> > Play chapter 1 episode 1 beat it and it will unlock. Thats how I got it.
>
> It’s only the second episode that isn’t working for me, not the first.
You’re not getting it.
If you’ve played, and beaten all the chapters for every episode but still haven’t received the achievement, then go back and play any of the chapters over again.
Many people are doing that and the achievement pops.
It happened to me. I played Ep 1, Ch 1 and once I completed it I got my achievement.
Cheers guys, I’ll do it tomorrow.