Problem when returning data via WS

I'm having trouble consuming the data from this WS.
The code I rode is working with another URL, but with this (http://api.promasters.net.br/cotacao/v1/valores) not returning the JSON data.
I tested this URL in the Postman just right and returned the data, but the code is not returning anything.

Could someone give me a hand and see what's going on?

Controller:

public class CotacaoDolar
    {
        double valorUsd;

        public double GetCotacao(double valorBrl)
        {
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("http://api.promasters.net.br/cotacao/v1/valores");

            CotacaoModel cotacao = new CotacaoModel();

            using (var response = (HttpWebResponse)request.GetResponse())
            {
                using (var reader = new StreamReader(response.GetResponseStream()))
                {
                    JavaScriptSerializer js = new JavaScriptSerializer();
                    var objText = reader.ReadToEnd();

                    cotacao = (CotacaoModel)js.Deserialize(objText, typeof(CotacaoModel));
                }
            }

            foreach (var item in cotacao.valores)
            {
                foreach (var val in item.usd)
                    valorUsd = val.valor;
            }

            var totalReais = valorBrl * valorUsd;

            return totalReais;
        }
    }

Model:

namespace Models
{
    public class USD
    {
        public string nome { get; set; }
        public double valor { get; set; }
        public int ultima_consulta { get; set; }
        public string fonte { get; set; }
    }

    public class EUR
    {
        public string nome { get; set; }
        public double valor { get; set; }
        public int ultima_consulta { get; set; }
        public string fonte { get; set; }
    }

    public class ARS
    {
        public string nome { get; set; }
        public double valor { get; set; }
        public int ultima_consulta { get; set; }
        public string fonte { get; set; }
    }

    public class GBP
    {
        public string nome { get; set; }
        public double valor { get; set; }
        public int ultima_consulta { get; set; }
        public string fonte { get; set; }
    }

    public class BTC
    {
        public string nome { get; set; }
        public int valor { get; set; }
        public int ultima_consulta { get; set; }
        public string fonte { get; set; }
    }

    public class Valores
    {
        public List<USD> usd { get; set; }
        public List<EUR> eur { get; set; }
        public List<ARS> ars { get; set; }
        public List<GBP> gbp { get; set; }
        public List<BTC> btc { get; set; }
    }

    public class CotacaoModel
    {
        public bool status { get; set; }
        public List<Valores> valores { get; set; }
    }
}