You will need to add in the full request and full response to the pp_checkout failure page. Here is the code to add to the page:
Here is the direct pay code also just in case you need that:
These values should be available to you in the bindings tab for the checkout. You can just drag and drop them onto the page wherever you would like to see them. If you have any further trouble with this or cannot determine what the error is telling you let us know and we will look into this with you.