Played a co-op mission with a friend, he was the host.  We both had to complete chapter 2, find the magos biologist.  When the mission was completed my friend received credit for completing the chapter, but the game wouldn't let me go to the next chapter as it said I didn't progress far enough in the game.  I tried to play the chapter 2 again in single player but the chapter 2 mission wasn't available to me or any of the other chapter missions. 

Is there  a way to bypass chapter 2 and allow me to play chapter 3?  Thanks!