Who works in V-Ray version lower than 3.1, be careful, in the materials in the BRDF section there is Microfaset GTR (GGX), if your version is older than 3.1, then the BRDF field will be empty. Choose Blinn, Phong or Ward - which is preferable for you. For Corona render, it is recommended to install a version not lower than 1.5, since the glossiness of the materials is adjusted taking into account PBR.