Mac OS won't let me launch the app to update. I need to get an updater.

I recently got this product and I love the idea of it. But, every time I try to convert a bought ITunes movie, it only converts the first five minutes of the movie. I have tried over a hundred times, dragging the file, clicking the file, EVERYTHING, and yet, it will still only come out converted with the first five minutes. This is very, very frustrating. How can I fix this? What am I doing wrong? How can I convert the entire movie? Please help!