Error in Posting To database

We have a Wordpress Ecommerce Site that uses a theme based shopping cart. There are 2 instances of this site( that is 2 domains) we recently implemented a new payment credit card payment gateway Payment Express for Credit card payments. This was working fine and is still accepting payments fine however after a sale is completed, it is now not posting the sale to the Theme back end Where we can manage and see new orders nor is it triggering the emails it should trigger to the Merchant and the customer. It seems the sale is still getting posted to the database but its not showing up nor triggering the emails as above. I need a change log of all files edited and all the work you have done for future reference/ documentation. Please only bid if you can get this done in 24 hours. You need to look into this and solve this within 24 hours, thanks for your time.