Were you able to add in the full request and full response bindings for the checkout on the failure page? This is the next step that needs to be taken to debug the problem further. You will need these bindings added to the page, if you also need the include files for them you can copy and paste the include files from your confirm page. Please post back with the results that you get after adding these bindings. If you post back with the info that appears on the page make sure to remove any sensitive details like PayPal logins or credit card numbers.