Bug 401 when using manually specified proxy on XP

#include "stdafx.h"
#include <string>
#include <cpprest\http_msg.h>
#include <cpprest\http_client.h>
#include <cpprest\uri_builder.h>
#include <conio.h>

using namespace std;
using namespace ::utility;
using namespace ::utility::conversions;


auto serviceUsername = U("cpprest@taxcom.ru");
auto servicePassword = U("123");

bool enableProxy = false;

auto proxyHost = U("localhost");                                    // Set your value please
auto proxyPort = 8888;                                              // Set your value please
web::http::client::credentials proxyLoginPassword(U("1"), U("1"));  // Set your value please

void initConfig(web::http::client::http_client_config& config)
{
    config.set_chunksize(64 * 1024);
    config.set_timeout(std::chrono::minutes(5));
    if (!enableProxy)
        return;
    web::uri_builder builder;
    builder.set_host(proxyHost);
    builder.set_port(proxyPort);
    web::http::client::web_proxy proxy(builder.to_uri());
    proxy.set_credentials(proxyLoginPassword);
    config.set_proxy(proxy);
}

string_t login()
{
    string_t token;
    auto uri = U("http://exw2k8r2/ExchangeAuth/api");
    auto X_TX_Username = U("X-TX-Username");
    auto X_TX_Password = U("X-TX-Password");
    auto User_Agent = U("User-Agent");
    web::http::client::http_client_config config;
    initConfig(config);
    web::http::client::http_client _client(uri, config);
    web::http::http_request req(web::http::methods::GET);
    req.set_request_uri(U("login"));
    req.headers().add(X_TX_Username, serviceUsername);
    req.headers().add(X_TX_Password, servicePassword);
    req.headers().add(User_Agent, U(""));
    token = _client.request(req).then([](pplx::task<web::http::http_response> previousTask)
    {
        try
        {
            auto response = previousTask.get();
            auto status = response.status_code();
            wcout << status << endl;
            if (response.status_code() == web::http::status_codes::OK)
            {
                auto json = response.extract_json().get();
                auto token = json.at(U("authtoken")).as_string();
                return token;
            }
        }
        catch (const web::http::http_exception& e)
        {
            auto desc2 = e.error_code().message();
            cout << desc2 << endl;
        }
        return string_t(U(""));
    }).get();
    wcout << token << endl;
    if (token.empty())
    {
        _getch();
        exit(-1);
    }
    return U("TaxcomToken token=\"") + token + U("\", realm=\"Exchange\"");
}

void getMessages(string_t Authorization)
{
    auto uri = U("http://exw2k8r2/Exchange/api");
    web::http::client::http_client_config config;
    initConfig(config);
    web::http::client::http_client _client(uri, config);
    web::http::http_request req(web::http::methods::GET);
    req.headers().add(web::http::header_names::authorization, Authorization);
    auto User_Agent = U("User-Agent");
    req.set_request_uri(U("messageList"));
    req.headers().add(User_Agent, U(""));
    _client.request(req).then([](pplx::task<web::http::http_response> previousTask)
    {
        try
        {
            auto response = previousTask.get();
            auto status = response.status_code();
            auto desc = response.extract_string().get();
            wcout << status << endl
                << desc << endl;
        }
        catch (const web::http::http_exception& e)
        {
            auto desc2 = e.error_code().message();
            cout << desc2 << endl;
            throw;
        }
    }).get();
}

int _tmain(int argc, _TCHAR* argv[])
{
    cout << "Try connect to server without proxy" << endl;
    try
    {
        auto Authorization = login();   //200 OK
        //Second request with special authorization token with req.headers().add(web::http::header_names::authorization, Authorization) :
        getMessages(Authorization);     //200 OK
    }
    catch (...)
    {
        cout << "Can't connect to server" << endl;
    }
    _getch();
    cout << "Try connect to server with proxy" << endl;
    enableProxy = true;
    try
    {
        auto Authorization = login();   //200 OK
        //Second request with special authorization token with req.headers().add(web::http::header_names::authorization, Authorization) :
        getMessages(Authorization);     //Bug Unauthorized 401 only on XP
    }
    catch (...)
    {
        cout << "Can't connect to server" << endl;
    }
    _getch();
}