Troubles with Post-request (Xnet)

[hangover228 0]

Im tried to auth on  but server responed me error 400 (Wrong Post-request). Im spend a lot of time to anylize that could be my problem but that tries didn't succsesive. Code is below:

Spoiler

 Uri url = new Uri("https://id.g2a.com/signin?client_id=g2a&redirect_uri=https://www.g2a.com/oauth2/token&response_type=code&auth_call=1&auth_json=1"); //post-data server (Sniffed by mozilla)
        using (var req = new HttpRequest())
        {
            req.AllowAutoRedirect = True;
            req.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:40.0) Gecko/20100101 Firefox/40.1";
            var param = new RequestParams
            {
                new KeyValuePair<string, string>("username", "TestLogin"), // login 
                new KeyValuePair<string, string>("password", "TestPassword"), // password
                new KeyValuePair<string, string>("security", "123123123"), // Captcha
                new KeyValuePair<string, string>("salt", "doLenFWI2v2oKEUnSNCf76oBj0kq4TgZDB8F%2F7bX7R4%3D"),
                // its changeable. Every requsts needs to have new defenition
                new KeyValuePair<string, string>("protection", "doLenFWI2v2oKEUnSNCf76oBj0kq4TgZDB8F/7bX7R4=")
                // its changeable. Every requsts needs to have new defenition
            };
            // place for keeping response
            Generator.KeeperAnsw = req.Post(url, param).ToString();
        }