Apple Pay - onvalidatemerchant Payment Not Completed error

I am implementing apple pay onto our website. I do not have a macOS device and am using windows visual studios / mvcnet. I have done all the merchantID and certification stuff and configured it on the windows machine. I am using Apple Pay JS and on the step where the payment sheet is opened with session.begin(). I use an ajax call to retrieve a merchantSession, which I believe it does successfully because the object consumed by session.completeMerchantValidation(merchantSession) contains an epochnumber, expiration time and the site name. However, immediately after completeMerchantValidation, the oncancel event is fired, and I get a red alert saying "Payment not completed".

I need help with how to proceed from here, I read somewhere online that the domain on where I am testing needs to be a registered merchant domain. For example, when I test the functionality of the button, I need to be on www.mySite.com, where I have mySite.com registered as a domain. Can someone confirm if this is true.. because I am accessing the site from my iOS devices through local IP address. If that is not true, any help proceeding from where I am would be helpful.

function StartPaySession() {
    var lineItems = [
        {
            label: 'Shipping',
            amount: '0.00',
        }
    ];

    var shippingMethods = [
        {
            label: 'Free Shipping',
            amount: '0.00',
            identifier: 'free',
            detail: 'Delivers in five business days',
        },
        {
            label: 'Express Shipping',
            amount: '5.00',
            identifier: 'express',
            detail: 'Delivers in two business days',
        }
    ];

    var total = {
        label: 'Apple Pay Example',
        amount: '8.99',
    };

    var paymentData = {
        countryCode: 'US',
        currencyCode: 'USD',
        shippingMethods: shippingMethods,
        lineItems: lineItems,
        total: total,
        supportedNetworks: ['amex', 'discover', 'masterCard', 'visa'],
        merchantCapabilities: ['supports3DS'],
        requiredShippingContactFields: ['postalAddress', 'email'],
    };


    var paySession = new ApplePaySession(2, paymentData);

    paySession.onvalidatemerchant = function (event) {
        var validationData = { ValidationUrl: event.validationURL };
        $.ajax({
            url: '/orders/cart/startapplepaysession',
            method: "POST",
            contentType: "application/json; charset=utf-8",
            data: JSON.stringify(validationData)
        }).then(function (merchantSession) {
            paySession.completeMerchantValidation(merchantSession);
            alert("end = " + window.location.host);
        }, function (error) {
            alert("merchant validation unsuccessful: " + JSON.stringify(error));
            paySession.abort();
        });
    };

    paySession.onpaymentmethodselected = function (event) {
        alert("1");
        paySession.completePaymentMethodSelection(total, lineItems);
    };

    paySession.onshippingcontactselected = function (event) {
        alert("2");
        paySession.completeShippingContactSelection(ApplePaySession.STATUS_SUCCESS, shippingMethods, total, lineItems);
    };

    paySession.onshippingmethodselected = function (event) {
        alert("3");
        paySession.completeShippingMethodSelection(ApplePaySession.STATUS_SUCCESS, total, lineItems);
    }

    paySession.onpaymentauthorized = function (event) {
        var token = event.payment.token;
        alert("payment authorization | token = " + token);
        paySession.completePayment(ApplePaySession.STATUS_SUCCESS);
    }

    paySession.oncancel = function (event) {
        alert("payment cancel error " + event);
    }

    paySession.begin();
};

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