SSL TCP SslStream Server выдает необработанное исключение System.Security.Cryptography.CryptographicException: невозможно найти исходную подписывающую сторону

Я пытаюсь создать TCP-сервер С# для получения данных TCP с помощью SslStream на сервере Windows 2008 от клиента (объективное мобильное приложение C), отправляющего данные TCP.

Я использую Microsoft пример кода (ПРИМЕЧАНИЕ: моя измененная версия этого кода находится в конце этого вопроса) т.е. это серверный код, сразу под строкой < strong>В следующем примере кода показано создание TcpListener, использующего класс SslStream для связи с клиентами.)

Исключение

Однако, когда я запускаю этот серверный код, я получаю следующее исключение:

System.Security.Cryptography.CryptographicException: Cannot find the original si
gner.

   at System.Security.Cryptography.CryptographicException.ThrowCryptographicExce
ption(Int32 hr)
   at System.Security.Cryptography.X509Certificates.X509Utils._LoadCertFromFile(
String fileName, IntPtr password, UInt32 dwFlags, Boolean persistKeySet, SafeCer
tContextHandle& pCertCtx)
   at System.Security.Cryptography.X509Certificates.X509Certificate.LoadCertific
ateFromFile(String fileName, Object password, X509KeyStorageFlags keyStorageFlag
s)
   at System.Security.Cryptography.X509Certificates.X509Certificate.CreateFromCe
rtFile(String filename)
   at SslTcpServer.LocationSslTcpServer.RunServer(String certificate) in c:\SslTcpServer\Program.cs:line 20
   at SslTcpServer.Program.Main(String[] args) in c:\SslTcpServer\Program.cs:line 180

Я также попробовал код в https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography.x509certificates.x509certificate?redirectedfrom=MSDN&view=net-5.0 и вызывает аналогичное исключение.

Дополнительная информация

Я получил свой SSL-сертификат от NameCheap. Я приобрел сертификат EssentialSSL Wildcard. Я сделал запрос на создание сертификата на сервере Windows 2008, т.е. получил текст, начинающийся с:

    -----BEGIN NEW CERTIFICATE REQUEST-----
            alots of random characters
    -----END NEW CERTIFICATE REQUEST-----

и загрузил этот текстовый файл в NameCheap и получил по электронной почте файл Certificate.cer.

Мой код

public sealed class LocationSslTcpServer
{
    static X509Certificate serverCertificate = null;
    // The certificate parameter specifies the name of the file 
    // containing the machine certificate.
    public static void RunServer(string certificate)
    {
        serverCertificate = X509Certificate.CreateFromCertFile(certificate);
        // Create a TCP/IP (IPv4) socket and listen for incoming connections.
        TcpListener listener = new TcpListener(IPAddress.Any, 8080);
        listener.Start();
        while (true)
        {
            Console.WriteLine("Waiting for a client to connect...");
            // Application blocks while waiting for an incoming connection.
            // Type CNTL-C to terminate the server.
            TcpClient client = listener.AcceptTcpClient();
            ProcessClient(client);
        }
    }
    static void ProcessClient(TcpClient client)
    {
        // A client has connected. Create the 
        // SslStream using the client's network stream.
        SslStream sslStream = new SslStream(
            client.GetStream(), false);
        // Authenticate the server but don't require the client to authenticate.
        try
        {
            sslStream.AuthenticateAsServer(serverCertificate,
                false, SslProtocols.Tls, true);
            // Display the properties and settings for the authenticated stream.
            DisplaySecurityLevel(sslStream);
            DisplaySecurityServices(sslStream);
            DisplayCertificateInformation(sslStream);
            DisplayStreamProperties(sslStream);

            // Set timeouts for the read and write to 5 seconds.
            sslStream.ReadTimeout = 5000;
            sslStream.WriteTimeout = 5000;
            // Read a message from the client.   
            Console.WriteLine("Waiting for client message...");
            string messageData = ReadMessage(sslStream);
            Console.WriteLine("Received: {0}", messageData);

            // Write a message to the client.
            byte[] message = Encoding.UTF8.GetBytes("Hello from the server.<EOF>");
            Console.WriteLine("Sending hello message.");
            sslStream.Write(message);
        }
        catch (AuthenticationException e)
        {
            Console.WriteLine("Exception: {0}", e.Message);
            if (e.InnerException != null)
            {
                Console.WriteLine("Inner exception: {0}", e.InnerException.Message);
            }
            Console.WriteLine("Authentication failed - closing the connection.");
            sslStream.Close();
            client.Close();
            return;
        }
        finally
        {
            // The client stream will be closed with the sslStream
            // because we specified this behavior when creating
            // the sslStream.
            sslStream.Close();
            client.Close();
        }
    }
    static string ReadMessage(SslStream sslStream)
    {
        // Read the  message sent by the client.
        // The client signals the end of the message using the
        // "<EOF>" marker.
        byte[] buffer = new byte[2048];
        StringBuilder messageData = new StringBuilder();
        int bytes = -1;
        do
        {
            // Read the client's test message.
            bytes = sslStream.Read(buffer, 0, buffer.Length);

            // Use Decoder class to convert from bytes to UTF8
            // in case a character spans two buffers.
            Decoder decoder = Encoding.UTF8.GetDecoder();
            char[] chars = new char[decoder.GetCharCount(buffer, 0, bytes)];
            decoder.GetChars(buffer, 0, bytes, chars, 0);
            messageData.Append(chars);
            // Check for EOF or an empty message.
            if (messageData.ToString().IndexOf("<EOF>") != -1)
            {
                break;
            }
        } while (bytes != 0);

        return messageData.ToString();
    }
    static void DisplaySecurityLevel(SslStream stream)
    {
        Console.WriteLine("Cipher: {0} strength {1}", stream.CipherAlgorithm, stream.CipherStrength);
        Console.WriteLine("Hash: {0} strength {1}", stream.HashAlgorithm, stream.HashStrength);
        Console.WriteLine("Key exchange: {0} strength {1}", stream.KeyExchangeAlgorithm, stream.KeyExchangeStrength);
        Console.WriteLine("Protocol: {0}", stream.SslProtocol);
    }
    static void DisplaySecurityServices(SslStream stream)
    {
        Console.WriteLine("Is authenticated: {0} as server? {1}", stream.IsAuthenticated, stream.IsServer);
        Console.WriteLine("IsSigned: {0}", stream.IsSigned);
        Console.WriteLine("Is Encrypted: {0}", stream.IsEncrypted);
    }
    static void DisplayStreamProperties(SslStream stream)
    {
        Console.WriteLine("Can read: {0}, write {1}", stream.CanRead, stream.CanWrite);
        Console.WriteLine("Can timeout: {0}", stream.CanTimeout);
    }
    static void DisplayCertificateInformation(SslStream stream)
    {
        Console.WriteLine("Certificate revocation list checked: {0}", stream.CheckCertRevocationStatus);

        X509Certificate localCertificate = stream.LocalCertificate;
        if (stream.LocalCertificate != null)
        {
            Console.WriteLine("Local cert was issued to {0} and is valid from {1} until {2}.",
                localCertificate.Subject,
                localCertificate.GetEffectiveDateString(),
                localCertificate.GetExpirationDateString());
        }
        else
        {
            Console.WriteLine("Local certificate is null.");
        }
        // Display the properties of the client's certificate.
        X509Certificate remoteCertificate = stream.RemoteCertificate;
        if (stream.RemoteCertificate != null)
        {
            Console.WriteLine("Remote cert was issued to {0} and is valid from {1} until {2}.",
                remoteCertificate.Subject,
                remoteCertificate.GetEffectiveDateString(),
                remoteCertificate.GetExpirationDateString());
        }
        else
        {
            Console.WriteLine("Remote certificate is null.");
        }
    }
    public static void DisplayUsage()
    {
        Console.WriteLine("To start the server specify:");
        Console.WriteLine("serverSync certificateFile.cer");
        Environment.Exit(1);
    }
}

class Program
{
    static int Main(string[] args)
    {
        string certificate = null;
  
        certificate = "Certificate.cer";
        try
        {
            LocationSslTcpServer.RunServer(certificate);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.StackTrace);
            Console.ReadLine();
        }
        return 0;

        
    }
}

Заранее спасибо за помощь!