I cannot see a course in D2L that I know I am registered for.
Courses become available to you in D2L as they are 'activated' by your instructor. Once a class is ready and activated, it will appear for you under your 'My Courses' widget. Timing on activation varies from instructor to instructor.
To see the classes you are officially registered for at anytime, you can log into iOnline and view your 'Class Schedule'.