This happens most often when there is a typo or mixing of the course and/or book code.
As a student, if you are required to use the Analytic Solver Platform you should receive both the course code and textbook code from your professor, our support team can not supply these directly to students.
Note: Your course code should end in a 2 digit year "indicator" and a one letter "semester indicator" (I.E. 18F would be for Fall of 2018). While this is not always the case, looking for something similar to this (any type of Year/Semester indication) can help differentiate the course code from the book code.
If you're a professor who has reached this page and are in need of a course code for your students, please email us at firstname.lastname@example.org to begin the process.