Once a course is FULL each manufacturer is notified and they can choose whether they want to open the course up to additional students. Sometimes this process can take days or weeks to re-open a course. In some cases, the manufacturer may choose to turn the course off rather than allowing additional enrollments.
A manufacturer contact is generally listed on the Details page for each course. You may contact them if you choose. If a contact isn't listed or you do not receive a response, please reach out to your university administrator.