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.