When you say you can't access the course does that mean you can't see the course on your Dashboard? If that's the case the course may not be published by your instructor yet, or your enrolment has not been finalised.
One thing you could try is to go to 'Courses' on the left hand side global navigation menu, then click on 'All Courses'. The list of all courses you are enrolled in will appear there. Simply fill in the star to the left of each course title that you would like to appear on your dashboard there.