VRay 1.5 for Rhino can't see material editor preview

Hello Rhino/VRay friends,

For some reason I can’t preview my materials before I render them. This has only recently developed and I can’t figure it out. Any suggestions? Thanks!

Do you have the “live update” checkbox clicked on for the preview.?
1.right click on the preview thumbnail and reload the MaterialPreviewScene.xml- if it is not there you have no material scene to render.
2.-reinstall. -usually helps.