I tried some examination and discovered that Circles defined with circle center point and used with pocked mill, don't render. I then discovered an exception; 1) define circle using circle center point 2) create contour with contour by pick, 3) Use pocket mill to create pocket. This process will create a pocket that will render. All of the variations I tried produce G code and the simulator will work on all.
In an effort to double check; I tried the above process using create contour by join polyline. It produced G code and the simulator will work but, it would not render.