Ti.Storekit Titanium Purchase Issue

I'm having an issue with the Storekit module in Titanium when buying a subscription based item (probably affects other items as well).

The error code that I get when buying the item is:

[WARN] error in transaction: Error Domain=SSServerErrorDomain Code=5002 "An unknown error has occurred" UserInfo=0x9b3a660 {NSLocalizedDescription=An unknown error has occurred}

requestProduct('553XXXXXX.testproductname', function (product) {
        var buySingleItem = Ti.UI.createButton({
            title: 'Buy ' + product.title + ', ' + product.formattedPrice,
            top: 60, left: 5, right: 5, height: 40
        });
        buySingleItem.addEventListener('click', function () {
            purchaseProduct(product);
        });
        win.add(buySingleItem);
    });

Tested with iPad Simulator and iPhone 4S running 5.1.1
Module is called Ti.Storekit version 1.5 
Titanium SDK version is 2.1.1