Correct Paypal IPN Error

We have a working Paypal IPN to process Paypal payments that verifies if the payment was made and then performs some steps to process the order. The IPN was perfectly working on our old server, yesterday we moved our website to a much better server but the IPN stopped working. We saw that Paypal tries to call it but the script doesn't process the payments. Also, we would like to add to the IPN the ability to Cancel approved orders once Paypal notifies the IPN of an unauthorized or canceled transaction. THIS MUST BE COMPLETED IN 7 HOURS MAX. We need the IPN working ASAP. ONLY PROFESSIONALS!