I need to login to my server via https put request. I have the certificate and key in my project but I still can’t seem to be able to login. My current code:

using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media.Imaging;
using Newtonsoft.Json;

namespace MyProject
{
    public class Login : Window
    {
        private TextBox ipAddressBox;
        private TextBox usernameBox;
        private PasswordBox passwordBox;
        private Button loginButton;
        private Button cancelButton;
        private ProgressBar progressBar;

    public Login()
    {
        Title = "Login";
        Width = 300;
        Height = 400;
        WindowStartupLocation = WindowStartupLocation.CenterScreen;

        var border = new Border
        {
            Padding = new Thickness(10),
            Child = CreateStackPanel()
        };

        Content = border;
    }

    private StackPanel CreateStackPanel()
    {
        var stackPanel = new StackPanel();

        var image = new Image
        {
            Source = new BitmapImage(new Uri("pack://application:,,,/MyProject;component/Assets/my_picture.png")),
            Height = 100,
            Margin = new Thickness(0, 0, 0, 10)
        };
        stackPanel.Children.Add(image);

        stackPanel.Children.Add(new Label { Content = "IP Address:" });
        ipAddressBox = new TextBox();
        stackPanel.Children.Add(ipAddressBox);

        stackPanel.Children.Add(new Label { Content = "Username:" });
        usernameBox = new TextBox();
        stackPanel.Children.Add(usernameBox);
        usernameBox.ToolTip = "username";

        stackPanel.Children.Add(new Label { Content = "Password:" });
        passwordBox = new PasswordBox();
        stackPanel.Children.Add(passwordBox);

        loginButton = new Button { Content = "Login", Margin = new Thickness(0, 10, 0, 0) };
        loginButton.Click += LoginButton_Click;
        stackPanel.Children.Add(loginButton);

        cancelButton = new Button { Content = "Cancel", Margin = new Thickness(0, 10, 0, 0) };
        cancelButton.Click += CancelButton_Click;
        stackPanel.Children.Add(cancelButton);

        progressBar = new ProgressBar { Visibility = Visibility.Hidden, Margin = new Thickness(0, 10, 0, 0) };
        stackPanel.Children.Add(progressBar);

        return stackPanel;
    }

    private void CancelButton_Click(object sender, RoutedEventArgs e)
    {
        Close();
    }

    private async void LoginButton_Click(object sender, RoutedEventArgs e)
    {
        string ipAddress = ipAddressBox.Text;
        string username = usernameBox.Text;
        string password = passwordBox.Password;

        if (ValidateIpAddress(ipAddress) && !string.IsNullOrEmpty(username) && !string.IsNullOrEmpty(password))
        {
            progressBar.Visibility = Visibility.Visible;
            string jsonResponse = await PerformLogin(ipAddress, username, password);
            progressBar.Visibility = Visibility.Hidden;

            MessageBox.Show(jsonResponse);

            Close();
        }
        else
        {
            MessageBox.Show("Enter valid IP address, username and password");
        }
    }

    private bool ValidateIpAddress(string ip)
    {
        return IPAddress.TryParse(ip, out _);
    }

    private async Task<string> PerformLogin(string serverIP, string username, string password)
    {
        try
        {
            // Load the certificate and private key from the Certs class
            X509Certificate2 clientCert = LoadCertificate(Certs.certPem, Certs.certKey);

            // Ensure the correct TLS version is used
            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;

            using (HttpClientHandler handler = new HttpClientHandler())
            {
                handler.ClientCertificates.Add(clientCert);
                handler.ServerCertificateCustomValidationCallback = (message, cert, chain, sslPolicyErrors) => true;

                using (HttpClient client = new HttpClient(handler))
                {
                    var json = new
                    {
                        username = username,
                        password = password,
                        is_start_up = true
                    };

                    string jsonString = JsonConvert.SerializeObject(json);
                    var content = new StringContent(jsonString, Encoding.UTF8, "application/json");

                    HttpResponseMessage response = await client.PutAsync($"https://{serverIP}:8443/login", content);

                    if (response.IsSuccessStatusCode)
                    {
                        string responseContent = await response.Content.ReadAsStringAsync();
                        var headers = response.Headers;

                        // Here, handle the response, extract tokens and update your application state

                        return "Logged in!";
                    }
                    else
                    {
                        string errorContent = await response.Content.ReadAsStringAsync();
                        return $"Login failed: {response.ReasonPhrase} - {errorContent}";
                    }
                }
            }
        }
        catch (HttpRequestException httpRequestEx)
        {
            return $"HttpRequestException: {httpRequestEx.Message}n{httpRequestEx.InnerException?.Message}";
        }
        catch (Exception ex)
        {
            return $"Exception: {ex.Message}n{ex.StackTrace}";
        }
    }

    private X509Certificate2 LoadCertificate(string certPem, string keyPem)
    {
        // Load the certificate
        byte[] certBuffer = Convert.FromBase64String(PemToBase64(certPem));
        var cert = new X509Certificate2(certBuffer);

        // Load the private key
        byte[] keyBuffer = Convert.FromBase64String(PemToBase64(keyPem));
        RSA rsa = CreateRsaProviderFromPrivateKey(keyBuffer);

        // Combine into a single X509Certificate2 object
        return cert.CopyWithPrivateKey(rsa);
    }

    private static string PemToBase64(string pem)
    {
        return pem
            .Replace("-----BEGIN CERTIFICATE-----", "")
            .Replace("-----END CERTIFICATE-----", "")
            .Replace("-----BEGIN RSA PRIVATE KEY-----", "")
            .Replace("-----END RSA PRIVATE KEY-----", "")
            .Replace("n", "")
            .Replace("r", "");
    }

    private RSA CreateRsaProviderFromPrivateKey(byte[] privateKey)
    {
        var rsaParameters = new RSAParameters();

        using (var ms = new MemoryStream(privateKey))
        {
            using (var reader = new BinaryReader(ms))
            {
                byte bt = 0;
                ushort twobytes = 0;

                twobytes = reader.ReadUInt16();
                if (twobytes == 0x8130) reader.ReadByte();
                else if (twobytes == 0x8230) reader.ReadInt16();
                else throw new Exception("Unexpected value in private key");

                twobytes = reader.ReadUInt16();
                if (twobytes != 0x0102) throw new Exception("Unexpected version");
                bt = reader.ReadByte();
                if (bt != 0x00) throw new Exception("Unexpected value in private key");

                rsaParameters.Modulus = reader.ReadBytes(GetIntegerSize(reader));
                rsaParameters.Exponent = reader.ReadBytes(GetIntegerSize(reader));
                rsaParameters.D = reader.ReadBytes(GetIntegerSize(reader));
                rsaParameters.P = reader.ReadBytes(GetIntegerSize(reader));
                rsaParameters.Q = reader.ReadBytes(GetIntegerSize(reader));
                rsaParameters.DP = reader.ReadBytes(GetIntegerSize(reader));
                rsaParameters.DQ = reader.ReadBytes(GetIntegerSize(reader));
                rsaParameters.InverseQ = reader.ReadBytes(GetIntegerSize(reader));
            }
        }

        var rsa = RSA.Create();
        rsa.ImportParameters(rsaParameters);
        return rsa;
    }

    private int GetIntegerSize(BinaryReader reader)
    {
        byte bt = 0;
        byte lowbyte = 0x00;
        byte highbyte = 0x00;
        int count = 0;

        bt = reader.ReadByte();
        if (bt != 0x02) return 0;

        bt = reader.ReadByte();
        if (bt == 0x81) count = reader.ReadByte();
        else if (bt == 0x82)
        {
            highbyte = reader.ReadByte();
            lowbyte = reader.ReadByte();
            byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
            count = BitConverter.ToInt32(modint, 0);
        }
        else
        {
            count = bt;
        }

        while (reader.ReadByte() == 0x00)
        {
            count -= 1;
        }
        reader.BaseStream.Seek(-1, SeekOrigin.Current);
        return count;
    }
}

}

With this code I get: “HttpRequestException: An error occurred while sending the request.
The request was aborted: Could not create SSL/TLS secure channel.”
Why could this be and how to fix this?