Can't login if I manually set cookies (HttpWebRequest)

Dim request As HttpWebRequest = DirectCast(WebRequest.Create("https://www.gumtree.com.au/t-login.html"), HttpWebRequest)
            Dim watempCookies As New CookieContainer

            request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; rv:58.0) Gecko/20100101 Firefox/58.0"
            request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
            request.Headers.Set(HttpRequestHeader.AcceptLanguage, "en-US,en;q=0.5")
            request.Headers.Set(HttpRequestHeader.AcceptEncoding, "gzip, deflate, br")
            request.Referer = "https://www.gumtree.com.au/t-login-form.html?sl=true"
            request.ContentType = "application/x-www-form-urlencoded"
            'request.Headers.Set(HttpRequestHeader.Cookie, "machId=Aw2aJbwGA2TDmD3-zY3nAc1hNmmT5I1E_Ous5nqpyQflA7ut1uPLvMaHyyRrzb15JMZHUt4LGFJx9VcvapvM83aI8S-UdFZShBU; up=%7B%_gid=GA1.3.2122029309.1519751089; _gali=btn-submit-login; _dm_sync=true; _gat=1")
            request.KeepAlive = True
            request.Headers.Add("Upgrade-Insecure-Requests", "1")

            request.CookieContainer = watempCookies

            request.Method = "POST"
            request.ServicePoint.Expect100Continue = False


            Console.WriteLine(" *** BEFORE *** ")

            Dim body As String = "ctk=D9M4moc8zISsord4tV2L3w&csrft=e99d2a8216130e33a130aa50c0d9595e&targetUrl=&likingAd=false&threatmetrixSessionId=3361643333039373432&loginMail=alphonseantonio%40gmail.com&password=Paenny127Naure8%2611&rememberMe=true&_rememberMe=on"


            Console.WriteLine(" *** AFTER *** ")


            Dim postBytes As Byte() = System.Text.Encoding.UTF8.GetBytes(body)
            request.ContentLength = postBytes.Length
            Dim stream As Stream = request.GetRequestStream()
            stream.Write(postBytes, 0, postBytes.Length)
            stream.Close()

            response = DirectCast(request.GetResponse(), HttpWebResponse)

            Console.WriteLine("Code : " & response.StatusCode & "  Description : " & response.ResponseUri.Query)


            watempCookies.Add(response.Cookies)
            'walogincookie = watempCookies

Try
ENTER ALL CODE HERE
Catch ex As WebException
MessageBox.Show(ex.Message & " - " & ex.StackTrace)
End Try