I can't send a get request

I set all the headers, and try to catch cookies, there are no cookies, the headers are set, the server still gives 404

var cookieContainer = new CookieContainer();
            HttpClientHandler handler = new HttpClientHandler() { CookieContainer = cookieContainer }; ;
            HttpClient client = new HttpClient(handler);
            client.DefaultRequestHeaders.Add("Referer", "https://www.icstrvl.ru/srch_v4/index.html");

            var html = await client.GetAsync("https://www.icstrvl.ru/srch_v4/index.html")
            Console.WriteLine(html);
// Получаю куки \/
            IEnumerable<Cookie> responseCookies13 = cookieContainer.GetCookies(new Uri(link)).Cast<Cookie>();
            foreach (Cookie cookiew1 in responseCookies13)
            {
                Console.WriteLine(cookiew1.Name + ": " + cookiew1.Value);
                cookieContainer.Add(cookiew1);
            }
// Устанавливаю заголовки \/
            var server = html.Headers.GetValues("Server").FirstOrDefault();
            var ETag = html.Headers.GetValues("ETag").FirstOrDefault();
            var Date = html.Headers.GetValues("Date").FirstOrDefault();

            client.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36");
            client.DefaultRequestHeaders.Add("Server", server);
            client.DefaultRequestHeaders.Add("ETag", ETag);
            client.DefaultRequestHeaders.Add("Date", Date);

            string link2 = "https://www.icstrvl.ru/srch_v4/json/sdata.json?city=538625&cnt=14472441&spo=0&ct%5B%5D=5&tt%5B%5D=65977793&transport=all_transports&ad=2&ch=0&infant=0&ml%5B%5D=1771&d%5B%5D=7&date=2020-07-31&date1=2020-07-31&cur=0&mp=&nonstop=1&gf=1&pg=1&ver=1455&__mthd=getSearchResult&lttt=1";
            var html2 = await client.GetAsync(link2);
            Console.WriteLine(html2);

If you run the code, you will see what headers and cookies are installed, after it returns 404, half a day I try to understand what is missing