¿Cómo agregar el certificado de cliente RestSharp en la solicitud Https? Mi código no funciona.

    public static IRestResponse<User> AsyncHttpRequestLogIn(string path, string method, object obj)
    {
        var client = new RestClient(Constants.BASE_URL + path); // https:....
        var request = method.Equals("POST") ? new RestRequest(Method.POST) : new RestRequest(Method.GET);
        request.RequestFormat = RestSharp.DataFormat.Json;

        // The path to the certificate.
        string certificate = "cer/cert.cer";     

        client.ClientCertificates.Add(new X509Certificate(certificate));

        request.AddBody(
            obj
        );


        IRestResponse<User> response = client.Execute<User>(request);

        return response;

    }