Blank page error when confirming bank transfer request

Hello,
We have installed the awocoupon component in a prestashop testing shop.
The problem is that when we confirm an order made by bank transfer of a product with gift certificate it gives blank page error and neither sends the coupon nor changes the state of product to CONFIRMED

a greeting

A blank screen implies there is a php error stopping execution.  Can you look in the php logs to see what the error was?  Happy to debug directly if you can send a private message with temp admin and ftp access.