Problem with UV editor

I have a problem concerning the uv editor. I use vray5 trial version in rhino7 trial version.
I have put a material in a textile object and I have set its mapping with UV editor. Also, i want this object to have opacity as it is a curtain. However, it doesnt show the opacity when I set UV editor. When I try the opacity in box mapping it doesn’t have any problem.

Do you have any idea why I have this problem?

Thank you very much