I have followed Jim Taylor’s example to create an involuted spur gear. I have completed the outline in Sketch mode but when I try to pull it into 3D there is no surface available to pull... Other geometry I’ve created has surfaces. ?????

I have followed Jim Taylor's video to create an involuted spur gear.  The geometry seems continuous and closed.  But when I try to pull it into a 3D solid there is no surface to pull. Other geometry I've created always has a surface to pull.  Am I missing something?