title: The request was aborted: Could not create SSL/TLS secure channel sandbox account
body: <p>It was working well before a week but now it shows following error. I have tried the following things but of no use. </p>
  
  <pre><code>ServicePointManager.Expect100Continue = true;
  ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;
  </code></pre>
  
  <p>so suggest me with possible solution </p>
  
  <pre><code>public string HttpCall(string NvpRequest) //CallNvpServer
      {
          string url = pendpointurl;
  
          //To Add the credentials from the profile
          string strPost = NvpRequest + "&amp;" + buildCredentialsNVPString();
          strPost = strPost + "&amp;BUTTONSOURCE=" + HttpUtility.UrlEncode(BNCode);
  
          ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;
          // allows for validation of SSL conversations
          ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
  
  
          HttpWebRequest objRequest = (HttpWebRequest)WebRequest.Create(url);
          objRequest.Timeout = Timeout;
          objRequest.Method = "POST";
          objRequest.ContentLength = strPost.Length;
  
          try
          {
              using (StreamWriter myWriter = new StreamWriter(objRequest.GetRequestStream()))
              {
                  myWriter.Write(strPost);
              }
          }
          catch (Exception e)
          {
              /*
              if (log.IsFatalEnabled)
              {
                  log.Fatal(e.Message, this);
              }*/
          }
  
          //Retrieve the Response returned from the NVP API call to PayPal
          HttpWebResponse objResponse = (HttpWebResponse)objRequest.GetResponse();
          string result;
          using (StreamReader sr = new StreamReader(objResponse.GetResponseStream()))
          {
              result = sr.ReadToEnd();
          }
  
          //Logging the response of the transaction
          /* if (log.IsInfoEnabled)
           {
               log.Info("Result :" +
                         " Elapsed Time : " + (DateTime.Now - startDate).Milliseconds + " ms" +
                        result);
           }
           */
          return result;
      }
  </code></pre>