Exception in ssl certificate code

I made a client server socket connection with sslStream but there is a a exception on server when the code reaches to line AuthenticateAsServer I searched in internet but I couldn't find a good answer why it happens. I made the .pfx testfile in my project and made a simple password for it. I don't know the problem is from file or not.

the exception is in line: sslStream.AuthenticateAsServer(certificate);

basic exception is: a call to sspi failed

inner exception is: clientsThe client and server cannot communicate, because they do not possess a common algorithm

server is a little long and I add the part of code that exception happens and all of client code:

this is server:

 public void AcceptCallBack(IAsyncResult ar) 
        {
        //    clients.Add(new myClient(server.EndAccept(ar)));
        //    try
       //     {
                myClient c = new myClient();

               // Socket handle = (Socket)ar.AsyncState;
                TcpListener handle = (TcpListener)ar.AsyncState;
                byte[] buff=new byte[2048] ;
               // Socket hand = handle.EndAccept(out buff,ar);
                TcpClient hand = handle.EndAcceptTcpClient(ar);
                dowork.Set();
                c.tcp = hand;
                clients.Add(c);
               // hand.BeginReceive(c.buffer, 0, c.buffer.Length, SocketFlags.None, new AsyncCallback(receiveIDCallBack), c);
                using (SslStream sslStream = new SslStream(hand.GetStream()))
                {
                    sslStream.AuthenticateAsServer(certificate);
                    // ... Send and read data over the stream
                    sslStream.BeginWrite(buff,0,buff.Length,new AsyncCallback(sendCallBack),c);
                    count++;
                    sslStream.BeginRead(c.buffer,0,c.buffer.Length,new AsyncCallback(receiveIDCallBack),c);
                }
       //     }
         //   catch(Exception)
          //  {

         //   }
        }//end of acceptcallback function

this is client:

using UnityEngine;
using System.Collections;
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Net.Security;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
public class sslCode : MonoBehaviour {


   // private Socket _clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    private byte[] _recieveBuffer = new byte[8142];

   static string server = "127.0.0.1";
    TcpClient client;

    public string message;
    public string receive;
    public string send;
    private void SetupServer()
    {
        try
        {

           // client.Connect(new IPEndPoint(IPAddress.Parse("127.0.0.1"), 1500));
            client = new TcpClient(server,1500);
            message = "connected";
        }
        catch (SocketException ex)
        {
            Debug.Log(ex.Message);
            message = ex.Message;
        }

       // _clientSocket.BeginReceive(_recieveBuffer, 0, _recieveBuffer.Length, SocketFlags.None, new AsyncCallback(ReceiveCallback), null);
        // Create a secure stream
        using (SslStream sslStream = new SslStream(client.GetStream(), false,
            new RemoteCertificateValidationCallback(ValidateServerCertificate), null))
        {
            sslStream.AuthenticateAsClient(server);

            // ... Send and read data over the stream
            sslStream.BeginRead(_recieveBuffer, 0, _recieveBuffer.Length, new AsyncCallback(ReceiveCallback),null);
        }

    }

    private bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
    {
        throw new NotImplementedException();
    }// end of setup server

    private void ReceiveCallback(IAsyncResult AR)
    {
        //Check how much bytes are recieved and call EndRecieve to finalize handshake
        using (SslStream sslStream = new SslStream(client.GetStream(), false,
       new RemoteCertificateValidationCallback(ValidateServerCertificate), null))
        {
            sslStream.AuthenticateAsClient(server);
            // ... Send and read data over the stream


            int recieved = sslStream.EndRead(AR);

            if (recieved <= 0)
                return;

            //Copy the recieved data into new buffer , to avoid null bytes
            byte[] recData = new byte[recieved];
            Buffer.BlockCopy(_recieveBuffer, 0, recData, 0, recieved);

            //Process data here the way you want , all your bytes will be stored in recData

            receive = Encoding.ASCII.GetString(recData);

            //Start receiving again
            sslStream.BeginRead(_recieveBuffer, 0, _recieveBuffer.Length, new AsyncCallback(ReceiveCallback), null);
        }
    }// end of receiveCallBack

    private void SendData(string dd)
    {
        using (SslStream sslStream = new SslStream(client.GetStream(), false,
       new RemoteCertificateValidationCallback(ValidateServerCertificate), null))
        {
          sslStream.AuthenticateAsClient(server);

            // ... Send and read data over the stream

            byte[] data = Encoding.ASCII.GetBytes(dd);
            SocketAsyncEventArgs socketAsyncData = new SocketAsyncEventArgs();
            socketAsyncData.SetBuffer(data, 0, data.Length);
           sslStream.BeginWrite(data,0,data.Length,new AsyncCallback(sendcallback),null);
            send = dd;
            sslStream.BeginRead(_recieveBuffer, 0, _recieveBuffer.Length, new AsyncCallback(ReceiveCallback), null);
        }
    }

    private void sendcallback(IAsyncResult ar)
    {

    }// end of send data

can this be problem of certificate file generated in vs or options of windows?

I searched a little more on internet and and I think there should be probability of algorithm mismatch that I use for my certificate file and what windows 8.1 can understand. i really don't know....

that algorithms that vs let me make for my certificate are "sha256RSA" and "sha1RSA" thanks for your help