"Dedicated to Crimson" achievement help

So, I’ve completed all five episodes, no achievement. I completed Episode Five through Spartan Ops matchmaking, does that not count?

Play through a chapter in Episode 5 by yourself. The achievement should pop after that.

Here’s hoping. Thanks for your time!

I had the same problem, I just played Spartan Ops Episode 1 Chapter 1 solo on easy. The achievement unlocked after completing the mission.