3d ribbon effect not working

[Kira27510234mq9o]

I'm just trying to create a 3b ribbon effect by drawing a curved line with the pencil tool, then going to extrude and bevel.  What the heck are those gray shapes in the ribbon???

[Ton Frederiks]

Is it a single path with no fill and only a stroke?

[Scott Falkner]

Expand the stroke (Object > Path > Outline Stroke), tehn apply the 3D effect.

[Ton Frederiks]

I don't think you need to expand, just a single extruded stroke will do.

[Ton Frederiks]

Can you share your problem file? Dropbox, CC file sharing, WeTransfer...