Payment page not receiving error handling

We have a payment form on one domain that submits to another. Everything is submitting fine but some of the errors are not coming through correctly for expiration date or card security code being wrong. We need the errors to show correctly, so that our customers may know why their card was declined. We are using [login to view URL] for the members area, and submitting the form from a different domain. We need this done today, its a very simple project. Looking for highly experienced PHP programmers who are also good at problem solving. More work to follow!