If, while enrolling, you are directed to your profile page, you most likely have missing data.
Take a look at the fields on the page, such as date of birth, phone number, etc. If any are blank, please enter the information requested and click the Update Profile button.
You should then return to the home page and attempt to enroll. After completing an enrollment, you can verify enrollment by checking if the class appears in My Courses by clicking the down arrow to the right of the words, My Courses. If your class(es) appear there, then you are enrolled.