I just finished the ODST campaign on Co-op just now. My partner got the “Nagato Makes Moving Easy” achievement (beating the campaign under 3 hours) but I didn’t.
We played the entire campaign together on Legendary. We both got a bunch of achievements (all the ones relating to beating a campaign on a certain difficulty) right after the campaign finished. Afterwards, we went into matchmaking and when we started searching for the match he got the Nagato achievement but I didn’t. My question is how can I fix this issue? I just checked the list and it does say that I still haven’t got the achievement.