Vray Materials not showing in the Rendered view port

I have an issue with Vray materials , I assign Materials normaly to each layer. But some materials are not shown in the rendered view, They appear as solid color blocks. Keep in mind that Im using Vray materials not external textures.

There is a known issue with the later service packs of Rhino 7 - it does not create the texture cache directory upon startup, which we expect to be present, where we write out the .jpg files for the original V-Ray .tx texture files.
As far as I can tell there are two workarounds:

  1. Install a bit older Rhino 7 version
  2. Delete the existing V-Ray material library and re-download. The newer version of the material library has its .tx files with JPG compression, and Rhino can open them.

A fix will be available in the next release

Im Already Using Rhino 6 and Vray 4

Hello, @majedmf1 ,
This most commonly occurs when а procedural V-Ray texture (not supported in Rhino’s viewport) is assigned to a material’s diffuse slot.
If this is not the case, could you please share a simple file (let’s say, a box with assigned material) to help us investigate the issue?

You can send a sample project by filling in the form at https://www.chaosgroup.com/help/contact/support/scene#options
Please be sure to include a link to this forum thread.

Kind regards,
Peter Chaushev
V-Ray for Rhino QA