paypal沙盒帐户响应失败

Question

我正在尝试测试将paypal集成到网站中。我在developer.paypal.com上创建了两个沙盒帐户，并确保两者都有足够的资金。

在下面的代码中，您会注意到逻辑。这笔钱从买家沙箱帐户中扣除，并且没有任何问题记入辅导员沙盒帐户（附上截图），但收到的回复是“失败”，这意味着我无法继续

    string authToken = "token provided";
    string txToken = Request.QueryString["tx"];
    string query = "cmd=_notify-synch&tx=" + txToken + "&at=" + authToken;

    //Post back to either sandbox or live
    string strSandbox = "https://www.sandbox.paypal.com/cgi-bin/webscr";
  //  string strLive = "https://www.paypal.com/cgi-bin/webscr";
    HttpWebRequest req = (HttpWebRequest)WebRequest.Create(strSandbox);

    //Set values for the request back
    req.Method = "POST";
    req.ContentType = "application/x-www-form-urlencoded";
    req.ContentLength = query.Length;
    //Send the request to PayPal and get the response
    StreamWriter streamOut = new StreamWriter(req.GetRequestStream(), System.Text.Encoding.ASCII);
    streamOut.Write(query);
    streamOut.Close();
    StreamReader streamIn = new StreamReader(req.GetResponse().GetResponseStream());
    string strResponse = streamIn.ReadToEnd();
    streamIn.Close();

    Dictionary<string, string> results = new Dictionary<string, string>();
    if (strResponse != "")
    {
        StringReader reader = new StringReader(strResponse);
        string line = reader.ReadLine();

        if (line == "SUCCESS")
        {

            while ((line = reader.ReadLine()) != null)
            {
                results.Add(line.Split('=')[0], line.Split('=')[1]);

            }
            Response.Write("<p><h3>Your order has been received.</h3></p>");
            Response.Write("<b>Details</b><br>");
            Response.Write("<li>Name: " + results["first_name"] + " " + results["last_name"] + "</li>");
            Response.Write("<li>Item: " + results["item_name"] + "</li>");
            Response.Write("<li>Item Number: " + results["item_number"] + "</li>");
            Response.Write("<li>Amount: " + results["payment_gross"] + "</li>");
            Response.Write("<hr>");
        }
        else if (line == "FAIL")
        {
            // Log for manual investigation
            Response.Write("Unable to retrive transaction detail");
        }
    }
    else
    {
        //unknown error
        Response.Write("ERROR");
    }

错误在“strResponse”中，我收到“失败”