Fix shopping cart for ecommerce website

My shopping cart was working fine before, then my web host had a hardware failure and restored a backup from a long time ago and now the shopping cart does not work. It does not add anything to the shopping cart, and I can't get to the checkout page or send the purchase through Authorize.net. I created the shopping cart a few years ago using an extension for Dreamweaver (Webassist eCart or WA_ecart) that no longer works. I need someone who can look at the PHP code and figure out what is is trying to do and why it isn't working, and help me fix it. It needs to take the selected item from the product list page (it does this already), add it to the shopping cart, and allow the user to check out and then enter credit card information through authorize.net. I have all of the pages that were working previously and I do not know why they are not doing anything now. If you need to see more pages or need additional information, please ask.