Pop up form is not working in version 3.4!

Hello… My pop up form is not showing up. Please take a look at: http://aprenderlyx.com/register/

And select any of them, is juts sending me to a this page http://aprenderlyx.com/wp-admin/admin-ajax.php?action=buynow&subscription=1, not a pop up!

Please help, my traffic is sending me complaints about the register form…