Ti.Storekit does not work

Hey there,

i have this script on a click event of my button:

function buyProVersion(e) {
 
            Storekit.addEventListener('transactionState', function (evt) {
                switch( evt.state ) {
                    case Storekit.FAILED:
                        alert("FAILED " + evt.productIdentifier);
                    break;
 
 
                    case Storekit.FAILED:
                        alert("FAILED " + evt.productIdentifier);
                    break;
 
                    case Storekit.PURCHASED:
                        //markProductAsPurchased(evt.productIdentifier);
                        alert("Purchased");
                    break;
 
                    case Storekit.PURCHASING:
                        alert("PURCHASING " + evt.productIdentifier);
                    break;
 
                    case Storekit.RESTORED:
                        alert("RESTORED " + evt.productIdentifier);
                    break;
                }
            });
 
 
        Storekit.receiptVerificationSandbox         = "production";
        Storekit.receiptVerificationSharedSecret    = "******";
 
 
        buyProVersion();
    }
 
    function buyProVersion() {
        Storekit.requestProducts(['*****'], function (evt) {
            if (!evt.success) {
                alert('ERROR: We failed to talk to Apple!');
            }
            else if (evt.invalid) {
                alert('ERROR: We requested an invalid product!');
            }
            else {
                purchaseProduct(evt.products[0]);
            }
        });
    }
 
 
    function purchaseProduct(product)
    {
        Storekit.purchase(product);
    }

But none of the Events are fired :/

The console prints out: "No event listener for 'transactionState' event"

Really frustrating :( - any idea?

Best, Nico