I just recently found out that some how i broke my game

Im level 37 basically doing a 100% walk threw main story played with a friend 1 time that was 30 levels ahead of me when I first started but ive completed most my own story. And my game is broke I don’t have gernade mod unlocked even though ive beat the story mission that unlocks it. is there anyway I can replay the mission and not have to completey restart my game?