apply 3D stroke to a shape layer?

hi all

I have some animated paths set up in a 3D scene, using shape layers (I used shape layers to have square capped lines instead of round caps:)

I wanted to try using 3D stroke, instead, to give a bit of thickness to these lines/paths... but I'm having trouble

Is it even possible to apply 3D stroke to a shape layer?  When I try it, the path just disappears (story of my life haha)

cheers

LML