Don't recieve PO., can any one help?

[Zakzoom]

I test my shopping cart by order and pay by western union, the system works perfect. But when i pay by credit cards, it seemed to work ok through the payment gateway company, except that i never get the perchase order from the shopping cart system. This problem happen since i changed the domain name and upgrade mysql server. The return url is correct, i do get confirm email from the payment gate way company. But i don't have order details and have to email to ask customers everytime. Any one know what are wrong or what scripts need to be fix?? Please help...

 

Zak