Shortcode to subscribe non users and enroll users

I need some help with shortocdes and custom pages in CoursePress Pro
I created my onw page /our-courses to display a list of courses
I am using Divi btw. So my plan was to use Divi to keep the pages looking consistent and then inject the shortocdes to run courses
Thus, I created Dashboard and Signup Pages and used shortcodes
I can ask you to tell me what shortcode do I use so that a non registered user can sign up and enroll and a registered user can enroll.
I am using:
[course show="image, title, summary, ,enrollment_dates, enrollment_type,cost,instructors,video," course_id="XXX"]
I have also tried this
[course show="title,summary,cost,button" course_id="XXX"]
In both cases after I signup using the form it opens the same form page and shows "Username already exists. Please choose another one."

When I checked in the Admin > Users section it shows the user as subscribed.