I didn't discover it until a friend tried to sign up for the course on the site, http://www.spirit-edu.com. It's the only course. The instructor and I always were logged in and access to the course and signing up through MarketPlace wasn't a problem.
When I went to sign up while not logged in, the screen just goes blurry and freezes until I go back to the previous page. Nobody can access the course to pay and therefore can't register.
Also, the overview for the course truncates at 46 characters. Way less than the example in the instructions.
I have had to delete almost all of the plugins that aren't yours, because they don't seem to play well with yours.
I am using Hostgator and a VPS server with only three websites on it. They are all wordpress. and very basic except this one.