Не отсылается POST data

                var request = (HttpWebRequest)WebRequest.Create("https://existing.site/some/script");
                request.Method = "POST";
                request.CookieContainer = cookies;
                request.UserAgent = "valid useragent here";
                request.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";
                request.Referer = "cool referer here";
                request.Headers["Origin"] = "origin here";
                var buffer = Encoding.UTF8.GetBytes(string.Join("&",
                    nvc.AllKeys.Select(key => String.Format("{0}={1}", key, HttpUtility.UrlEncode(nvc[key])))));
                request.ContentLength = buffer.Length;
                using (var stream = request.GetRequestStream())
                {
                    stream.Write(buffer, 0, buffer.Length);
                }
 
                using (var response = (HttpWebResponse)request.GetResponse())
                {
                    result = JObject.Parse(response.GetResponseText(Encoding.UTF8));
                }

            var buffer = new UTF8Encoding(false).GetBytes(string.Join("&",
                nvc.AllKeys.Select(key => String.Format("{0}={1}", key, HttpUtility.UrlEncode(nvc[key])))));