Closed polyline curve, bounding box, super T AS5100

Please find attached a definition that generats a varying section along a curve.

I have amended the section to create an asymmetric section named end section.

I am able to generate a surface from the defining curve, however when I call up the curve it is saying that it is open. The curve has been constucted from  lines and polyline curves.

Can someone provide some info as to close the curve. I'm not sure if its sloppy geometry, i cannot track down the issue.

regards

Kenyon