The types of error message you may receive are:
The Course ID you entered was not found. Please re-enter the course ID provided by your instructor. If you continue to receive this error message please advise your instructor.
Or you may notice that your code registers you for the wrong course or receive the following error when trying to join your Mastering online course:
Your Subscription to Mastering does not include access to the book for this course.
Please check the course ID and try again.