Your ellipsis coordinates are incorrect, that should be (x1, y1, x2, y2), where x1 <= x2 and y1 <= y2, as those pairs, (x1, y1) and (x2, y2), represents respectively top left and bottom right corners of enclosing rectangle.
Try to change to
draw.ellipse((20, 20, 180, 180), fill = 'blue', outline ='blue')
