@panixia said:

@bocomofo said:

have you checked the use 'colour texture as transparency' in the diffuse rollout.

he did it for sure, elsewhere transparency would have not worked in the diffuse 👍
I would rather check if the material was properly applied to the backface, cause that can lead some problem. i suggest check if the material is applied on the front face (turn on monocrhome mode and check) and then use "frontface material to backface" from thomthom's UV Toolkit

👍 That sounds like the right answer.
I did some quick tests - and if you have a different material on the backface, the shadow will be a half-tone of the transparency of the front and the opacity of the back.