is it possible that I have done something that makes this surface not a NURBS surface anymore? I started with a NURBS surface and having been tweaking hulls and CV's, but I'm still not able to insert an isoparm and have been trying other things also. I just tried to modify-convert-to subdiv and it told me to open the script editor for the error. The errors are as follows:

nurbsToSubdiv -rn false -mp true -ch off -aut on -maxPolyCount 1348 |group1|organic_head:nurbsCylinder1|organic_head:n urbsCylinderShape1;
// Warning: nurbsToSubdiv1 (Nurbs To Subdiv Node): invalid input NURBS surface. //
// Error: Command nurbsToSubdiv failed. Open Script Editor for details. //

WHAT HAVE I DONE?