PC/MCC/Reach
I started the campaign on legendary and always played solo. Beat the game the same way, legendary and solo, about an hour ago. However, both the achievements for beating the campaign on legendary and the one for beating it legendary solo are both stuck on 8/9 in the achievement section of the career menu. I went through the campaign menu and made sure that the shown difficulty that I beat the level on was legendary, and they all were.
Verified the file integrity on Steam and still no luck.
UPDATE: For some reason, Long Night of Solace didn’t register as being beaten at all despite showing that it was beaten on Legendary in the MCC. Recompleting it. Hopefully that will fix the issue.
UPDATE: Rebeat the mission and unlocked the achievements.