I have completed the entire campaign on 4 player coop, have a check mark by every act, the progress bar is all the way full, but it does not give me credit for this achievement. Any ideas?
This issue has come up before. Most people just replayed the first mission, some people had to replay the last mission. Thats as much as I know about it. If that doesn't help I'd try gearsforums.epicgames.com