Course unit next button redirect to 404 page

I'm having the exact same issue as the person who posted this https://premium.wpmudev.org/forums/topic/course-completion-page-give-404-not-found-error

I updated everything to the newest version and the issue persists, so I had to roll back because the newest version of CoursePress also caused other issues.
I have currently version: 2.0.5 installed.

Go to this link and click next to see the error : https://marchingartseducation.com/courses/tuning-just-intonation-matt-harloff/units/athletic-training-ralph-reiff-and-matt-harloff