Surfsect SOP not working

I’ve been trying to get the Surfsect SOP working with two simple circles that are set to NURBS or Bezier Curve more. Nothing I do works. Grouping the circles, Intersect, union,… nothing happens. All I see is dots where the points of the second input are and the output is the exact same as the input. Can anyone give me an idea of what I might be doing wrong? Thanks