RRT

So, my nova up and decided to no longer feed. I cleaned the mag tube and tried it out with some dummy rounds before I assembled the entire shotgun, and it fed flawlessly. I then re-assembled it and tried it again and it no longer feeds. As an experiment I took the barrel off and now it feeds, barrel back on.....nothing! As far as I can tell there is nothing wrong with the barrel. Any Ideas on how to fix this?