Upon completing the Halo 2 Campaign on Legendary, I not only didn’t receive an achievement but I didn’t get any general unlocks such as a nameplates. This is absurd, since each campaign says highest rank completed is Legendary. I can link a OneDrive video should this require evidence but I can’t be the only one having this issue.
I’m having the same problem. I was using the nonscoring skulls and when I was about to load the last mission in halo 2 it said something like “are you sure you want to start the mission, you have a point multiplier of 0.00, any achievements, or points will not be saved”. I’m not sure if this is the problem, it’s just a guess. Please don’t criticize me on trying tho remake the message because it’s late and my memory is kind of foggy. Hope this helps!