1. Did you check the day you are currently viewing is the correct one? If you planned courses that start in September and now it's summer, you will have to select the correct day!  
  2. Did you check that there are no closures on the day you are viewing? If you planned closures, there won't be classes on the day/period of planned closure! You can check from Planning -> Courses -> Closures
  3. Did you make sure you have waited enough after the the planning of the courses? Usually the Timetable doesn't update immediately, it takes up to 10/15 minutes for courses to show on it. If you did wait, then click on Planning -> Courses -> Course Summary and select the necessary season. Click on update and then select the courses that you didn't find on the timetable.  Click on Planning -> Reschedule Selected Courses.