Im recently playing H2A, and in on Delta Halo but steam didn’t give me previous missions achievements.
I only unlocked the first mission achievement and the Chips Dubbo one.
The question is, i have to replay those missions on legendary AGAIN?!
That would be a huge torture.
Achievements related to par time/score and level completion have issues if your data doesn’t get synced properly with Halo Waypoint. In such cases, replaying the level is the only way to get the achievement to unlock.
I’m having the same issue on H2A with co-op on a Series X