I had same problem when I tried to upgrade using the Safari on iPad. I would suggest try to upgrade on a different tool (phone, computer, iPad, etc). Once I have paid for the course, I had no problem accessing the materials on iPad, iPhone, or Mac.
Have you tried hitting CTRL - (that's the minus key) to zoom out or looking at it in another browser or on another computer? I'm thinking this is a settings issue. Looks good to me on my screen - no fuzzies or pixelation.