Can't retake quiz?

Hi All,

I have 3 modules (scenes) with a quiz at the end of each scene with an "unlimited" ability to answer each question right. The first time through, you can take the quiz and it appears to work, but you can’t go back and re-take it (It doesn’t let you select the answers)  

This isn't a problem if someone goes all the way through, but it might be if the skip a module and go back.  When I restarted from the beginning, it worked fine again and I was able to take the quiz but I had to refresh the browser.  

Is there a way I can set it up so the user can go back and retake any of the quiz questions?