Hi Saguaros,
Thanks for sending the screen cap.
Please note that you are not being logged in and taken to the page of the course. You are seeing the home of the web loaded inside the modal window. Notice that the blue X to close the modal is still at the top right. If you close the modal you'll see the user has not been logged in and has not been enrolled in the course.
What should happen is that the user is logged in, the modal is closed, and the user is taken to the course page, having been enrolled in it.
Thank you for your help.
Best,
Roger.