Не могу авторизоватся

private CookieContainer GetCookis(string uriCooki, string acount = null)
        {
            CookieContainer cooc = new CookieContainer();
            try
            {
                ServicePointManager.Expect100Continue = false;
                authReq = (HttpWebRequest)WebRequest.Create(uriCooki);
                authReq.CookieContainer = cooc;
                authReq.Method = "POST";
                authReq.AllowAutoRedirect = false;
                authReq.UserAgent = "Opera/9.80 (Windows NT 6.1; Win64; x64) Presto/2.12.388 Version/12.15";
                authReq.ContentType = "application/x-www-form-urlencoded";
                byte[] bPost = Encoding.GetEncoding(1251).GetBytes(acount);
                authReq.ContentLength = bPost.Length;
                authReq.GetRequestStream().Write(bPost, 0, bPost.Length);
                authReq.GetRequestStream().Close();
                contRes = (HttpWebResponse)authReq.GetResponse();
                return authReq.CookieContainer;
            }
            catch (Exception exGetCookis)
            {
                return null;
            }
        }