URGENT Fix Paypal Payments Pro Magento Integration Today

We are using paypal web payments pro to take payments on our magento site. The API credentials are all put into the configuration panel and Paypal Express works fine. The only issue is that when you click place order after entering your credit card details you are just redirected to the shopping cart. No error message, no payment taken, no order registered. We need this fixing urgently, today. So someone who knows how to deal with this issue is required.