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 of at least 1.5, since the glossiness of materials is adjusted taking into account PBR

Enjoy your use =)