Most teachers will ask you to join a course. This allows them to view your work. To do this, you will need a "Course ID," which your teacher will give to you.
Check with your teacher to make sure you have the correct Course ID and if he or she has made the course available to students.
The Course ID is case sensitive so be sure to enter each character exactly as it appears.
If none of the above steps have solved the issue, it is possible you have registered under the wrong product, and therefore do not have access to your teacher's course. Confirm with your teacher which product you should be using.