You see this:
The course ID you entered is for a LMS-linked course. You must register for this course through your local campus version of the LMS learning management system (LMS).
Please contact your instructor if you do not have the LMS web address.
You don't need a course ID or invite link. Open your My Lab or Mastering course from your LMS course to register. Otherwise, your grades might be incorrect.
To fix this, close the tab or window and start the registration from your LMS course.