I'm using Paypal in sandbox mode to check my configuration but it doesn't seem to work.
The order is processed by Paypal, in the account the of buyer money is deducted and merchant receives the money but Prestashop just returns the user to Order history page with item or items still in shopping cart.
Prestashop version is 220.127.116.11 and PayPal USA, Canada module is 1.3.3
I tried with debug mode, compatibility warnings, and debug profiling. I get no new information other than profiling data, no warnings no errors.