Sorry to know that new ratings haven't reflected in your course even after 48 hrs..At this point, we can only wait for few more hours to see if you see them. Appreciate your patience!
Also, please note that only those ratings appear on the landing page of the course and count towards the overall rating of your course which pass the spam filter of Udemy: which Udemy's algorithm considers as genuine ratings. Also, such genuine ratings need written comments/feedback - only then they appear on the landing page. This helps the prospects/future students make an informed decision before they purchase your course.
Hope this clarifies!