Transparency showing in shadows

I have a built a wooden frame in 3ds max with square cutouts and patched them with fabric. The frame is dark brown.

The fabric patches are single surfaces using a light brown vray material, but the 2 at the front use one called canvas transparent

When I look at the shadow beneath the frame the light does not appear to pass through the transparent material. The shadow is the same for materials called canvas and canvas transparent despite the fact the transparent one has the refraction set to 205,205,205, in the material editor

How do I make the material transmit light due to its transparency, what settings do I need?

thanks

Nigel

Maybe that ?

thanks very much