Strona HomeControler / Index.cshtml jest jak poniżej

<div id="paypalDiv">

        <form id="paypalForm" action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post">
            <fieldset>
                <p class="inline-small-label" style="padding-top: 7px;">
                    <label for="device-id"><span>User ID</span></label></p>

                <input id="custom" class="full-width" type="text" name="custom" value="">
                <input class="full-width" type="hidden" name="business" value="[email protected]">
                <input type="hidden" name="cmd" value="_xclick">
                <input type="hidden" name="item_name" value="credits">
                <input type="hidden" name="item_number" value="40">
                <input type="hidden" name="amount" value="2.95">
                <input type="hidden" name="no_shipping" value="1">
                <input type="hidden" name="return" value="http://localhost:13769">
                <input type="hidden" name="notify_url" value="https://localhost:13769/Home/Ipn">
                <button class="btn btn-primary submit-button" type="submit">Pay with PayPal</button>
            </fieldset>

        </form>
    </div>

Metoda HomeControler / Ipn Action jest jak poniżej

public ActionResult Ipn()
{
    // Receive IPN request from PayPal and parse all the variables returned
    var formVals = new Dictionary<string, string>();

    formVals.Add("cmd", "_notify-validate");

    // if you want to use the PayPal sandbox change this from false to true
    string response = GetPayPalResponse(formVals, false);

    if (response == "VERIFIED")
    {
        string transactionID = Request["txn_id"];
        string sAmountPaid = Request["mc_gross"];
        string deviceID = Request["custom"];

        //validate the order
        Decimal amountPaid = 0;
        Decimal.TryParse(sAmountPaid, out amountPaid);

        if (sAmountPaid == "2.95")
        {
            // take the information returned and store this into a subscription table
            // this is where you would update your database with the details of the tran

            return View();

        }
        else
        {
            // let fail - this is the IPN so there is no viewer
            // you may want to log something here
        }
    }

    return View();
}

Moje pytanie jest nawet po dokonaniu płatności, powyżej metody akcji IPN nie odpala. Nie można debugować. Jak mogłem to zrobić?