Who works with V-Ray version “lower than 3.1, pay attention to materials section BRDF (microfaset GTR (GGX)), if your version is older than 3.1 - this section will be empty, and you have to choose: Blinn, Ward or Phong, d dependence on material. "

For Corona render, it is “recommended to install a version of at least 1.5, since the glossiness of materials is configured considering PBR.”