Don't know if this has been brought up yet, looked through the posts. I have attempted the campaign twice now. The first time after completing a few missions, I decided to go without the default loadout and change up my primary weapon. When I made the adjustments I went back to start the mission and it would not let me start the mission. I went back into the loadout and set it back to default. Tried again and it would not let me start. I went back in the menu and now the only option is to start a new story.