On a Kinterathon, you can create multiple registration type or different fees for the participant to select from. Sometimes some of the registration types although existed on the backend, but they are missing from the registration form.
In this case, check for two things:
1. Check if the registration type is setup for backend registration only (Sphere Only) a. Go to Communities > Special Events > Friends Asking Friends > Kintera Thon > b. Hover over the event name > Click Website Info > Click Fee Structure c. See if 'Sphere Only' option is selected
2. Check to see if there is an end date setup to stop accepting registration