Please help me make paypal IPN work!

[arcon5]

I am using the code below for paypal notifications.

I checked the notification history and it comes back as payment_status is Complete BUT the VB code performs the code for the "INVALID" case...

Any pointers would be most appreciated...............

  'Post back to either sandbox or live
        Dim strSandbox As String = "https://www.sandbox.paypal.com/cgi-bin/webscr"
        Dim strLive As String = "https://www.paypal.com/cgi-bin/webscr"
        Dim req As HttpWebRequest = CType(WebRequest.Create(strSandbox), HttpWebRequest)

        'Set values for the request back
        req.Method = "POST"
        req.ContentType = "application/x-www-form-urlencoded"
        Dim Param() As Byte = Request.BinaryRead(HttpContext.Current.Request.ContentLength)
        Dim strRequest As String = Encoding.ASCII.GetString(Param)
        strRequest = strRequest + "&cmd=_notify-validate"
        req.ContentLength = strRequest.Length

        'for proxy
        'Dim proxy As New WebProxy(New System.Uri("http://url:port#"))
        'req.Proxy = proxy

        'Send the request to PayPal and get the response
        Dim streamOut As StreamWriter = New StreamWriter(req.GetRequestStream(), Encoding.ASCII)
        streamOut.Write(strRequest)
        streamOut.Close()
        Dim streamIn As StreamReader = New StreamReader(req.GetResponse().GetResponseStream())
        Dim strResponse As String = streamIn.ReadToEnd()
        streamIn.Close()
        Dim order_item_no, order_trans_id, order_pay_status As String
        order_item_no = Request.Form("item_number1")
        order_trans_id = Request.Form("txn_id")
        order_pay_status = Request.Form("payment_status")
        If strResponse = "VERIFIED" Then
            'check the payment_status is Completed
            'check that txn_id has not been previously processed
            'check that receiver_email is your Primary PayPal email
            'check that payment_amount/payment_currency are correct
            'process payment
            If order_pay_status = "Completed" Then

                If Mid(order_item_no, 1, 1) = "Z" Then
                    order_item_no = order_item_no.Replace("Z", "")
                    Call GetInvoiceDetails("", "", "", order_item_no, "")
                    Call DBgeneral("UPDATE tblInvoice SET invPaid='1' WHERE invID=" & order_item_no & ";")
                    Call DBgeneral("INSERT INTO tblInvoiceInfo(iiInvoiceID,iiType,iiReference,iiNote) VALUES('" & order_item_no & "','1','" & order_trans_id & "','PayPal Payment made!');")
                    Call SendMail(InvUser(0), "Payment received with thanks!", "1", "payment_received", order_item_no, "")
                    If InvStatus(0) = "0" Then
                        Call DBgeneral("UPDATE tblInvoice SET invStatus='1' WHERE invID=" & order_item_no)
                    End If
                End If
            Else

            End If
            Call SendMail("", "Completed:Order PPI", "0", "Order ID:" & order_item_no & " <p>Completed<p>", "", "")

        ElseIf strResponse = "INVALID" Then
            'log for manual investigation
            ' Call SendMail("", "Invalid:Order PPI", order_item_no & "<p>" & order_trans_id, "", "")
            Call SendMail("", "INVALID:Order PPI Response:" & strResponse, "0", "Order ID:" & order_item_no & " <p>Completed<p>", "", "")
        Else
            'Response wasn't VERIFIED or INVALID, log for manual investigation
            ' Call SendMail("", "Other:Order PPI", order_item_no & "<p>" & order_trans_id, "", "")
            Call SendMail("", "ELSE:Order PPI", "0", "Order ID:" & order_item_no & " <p>Completed<p>", "", "")
        End If
        '  Call SendMail("", "API LOAD0", "0", "Order ID:" & order_item_no & " <p>Completed<p>", "", "")
        Call SendMail("", "API DATA", "0", strResponse, "", "")