title: The request was aborted: Could not create SSL/TLS secure channel.System.Net.WebException
body: <p>I am using PayPalStandard plugin of NopCommerce. When I placed the order &amp; make payment with paypalstandard plugin after successful payment on paypal, it redirects to merchants site. At that time it gives error:</p>
  
  <blockquote>
    <p>The request was aborted: Could not create SSL/TLS secure channel.</p>
  </blockquote>
  
  <p>Also I am using Sandbox account of Paypal for testing.</p>
  
  <p>It throws error from this line: </p>
  
  <pre><code>var sw = new StreamWriter(req.GetRequestStream()
  </code></pre>
  
  <p>Here is code below:</p>
  
  <pre><code>var req = (HttpWebRequest)WebRequest.Create(GetPaypalUrl());
          req.Method = "POST";
          req.ContentType = "application/x-www-form-urlencoded";
          req.ProtocolVersion = HttpVersion.Version10;
  
          string formContent = string.Format("cmd=_notify-synch&amp;at={0}&amp;tx={1}", _paypalStandardPaymentSettings.PdtToken, tx);
          req.ContentLength = formContent.Length;
  
          using (var sw = new StreamWriter(req.GetRequestStream(), Encoding.ASCII))
              sw.Write(formContent);
  </code></pre>