I'm having trouble adding a Tea Commerce extension. I've followed http://rune.gronkjaer.dk/en-US/2010/11/26/how-to-use-the-tea-commerce-events/ whilst setting it up however it's not calling 'Initialize()' (or as far as I can tell its not) so I'm wondering what I'm doing wrong, the class is supposed to add shipping by weight into the shop however the shipping price isnt updated. Here's my code:

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Web;
using System.Xml.XPath;
using TeaCommerce.Data;
using TeaCommerce.Data.Extensibility;
using TeaCommerce.Data.Tools;

/// 
/// Summary description for TeaCommerceExtension
/// 
namespace TeaCommerce.WebShop.Integration
{
    public class TeaCommerceExtension : ITeaCommerceExtension
    {
        #region ITeaCommerceExtension Members

        public void Initialize()
        {
            WebshopEvents.OrderLineChanged += WebshopEvents_OrderLineChanged;
            WebshopEvents.ShippingMethodChanged += WebshopEvents_ShippingMethodChanged;
            WebshopEvents.CurrencyChanged += WebshopEvents_CurrencyChanged;
            WebshopEvents.OrderLineRemoved += WebshopEvents_OrderLineRemoved;
        }


        void WebshopEvents_OrderLineRemoved(Order order, OrderLine orderLine)
        {
            UpdateOrderShippingCost(order);
        }

        /// 
        /// On currency change
        /// 
        /// 
        /// 
        void WebshopEvents_CurrencyChanged(Order order, Currency currency)
        {
            UpdateOrderShippingCost(order);
        }

        /// 
        /// On shipping method change
        /// 
        /// 
        /// 
        void WebshopEvents_ShippingMethodChanged(Order order, ShippingMethod shippingMethod)
        {
            UpdateOrderShippingCost(order);
        }

        void WebshopEvents_OrderLineChanged(Order order, OrderLine orderLine)
        {
            UpdateOrderShippingCost(order);
        }

        #endregion

        private void UpdateOrderShippingCost(Order order)
        {
            XPathNodeIterator allXml = umbraco.library.GetXmlAll();

            XPathNavigator shippingRules = allXml.Current.SelectSingleNode("//Shipping Rules");
            decimal defaultWeightInKg = (decimal)PriceHelper.ParsePrice(shippingRules.SelectSingleNode("defaultWeight").Value);

            decimal totalWeightInKg = 0;
            foreach (OrderLine ol in order.OrderLines)
            {
                OrderLineProperty weightProp = ol.Properties.FirstOrDefault(p => p.Alias == "productWeight");
                if (weightProp != null && !string.IsNullOrEmpty(weightProp.Value))
                    totalWeightInKg += (decimal)PriceHelper.ParsePrice(weightProp.Value.ToString()) * ol.Quantity;
                else
                    totalWeightInKg += defaultWeightInKg * ol.Quantity;
            }

            XPathExpression weightPathXPath = XPathExpression.Compile("./weightRange");
            weightPathXPath.AddSort("upToWeight", XmlSortOrder.Ascending, XmlCaseOrder.None, string.Empty, XmlDataType.Number);

            XPathNodeIterator weightRules = shippingRules.Select(weightPathXPath);
            decimal shippingPricePerKgWithoutVAT = 0;
            while (weightRules.MoveNext())
            {

                if (PriceHelper.ParsePrice(weightRules.Current.SelectSingleNode("upToWeight").Value) >= totalWeightInKg)
                {
                    shippingPricePerKgWithoutVAT = (decimal)PriceHelper.ParsePrice(weightRules.Current.SelectSingleNode("shippingPrice" + order.Currency.ISOCode).Value);
                    break;
                }
            };


            decimal totalShippingPriceWithoutVAT = shippingPricePerKgWithoutVAT * totalWeightInKg;

            OrderProperty shippingPriceOP = order.Properties.FirstOrDefault(p => p.Alias == "shippingPriceWithoutVAT" + order.Currency.ISOCode);
            OrderProperty totalWeightInKgProp = order.Properties.FirstOrDefault(p => p.Alias == "totalWeightInKg");
            if (shippingPriceOP == null)
            {
                shippingPriceOP = new OrderProperty("shippingPriceWithoutVAT" + order.Currency.ISOCode, totalShippingPriceWithoutVAT.ToString());
                order.AddProperty(shippingPriceOP);
                totalWeightInKgProp = new OrderProperty("totalWeightInKg", totalWeightInKg.ToString());
                order.AddProperty(totalWeightInKgProp);
            }
            else
            {
                if (Decimal.Parse(shippingPriceOP.Value) != totalShippingPriceWithoutVAT)
                    shippingPriceOP.Value = totalShippingPriceWithoutVAT.ToString();

                if (Decimal.Parse(totalWeightInKgProp.Value) != totalWeightInKg)
                    totalWeightInKgProp.Value = totalWeightInKg.ToString();
            }
            if (order.ShippingMethod.Id == 2 && order.ShippingFeeWithoutVAT != totalShippingPriceWithoutVAT)
                order.ShippingFeeWithoutVAT = totalShippingPriceWithoutVAT;

            order.Save();
        }
    }
}