Woo PDF Product Vouchers producing blank pdfs after update

After the recent Woo update and subsequent update of the PDF Product Vouchers plugin blank pdfs are being generated. The install of a voucher on a new site (for a different client) was working until a second update of the plugin and now that has rendered existing voucher templates uneditable.
I’ve now been waiting four days for a reply to a support ticket so am turning to the forum for help. Has anyone else experienced this problem and got a response/found a work around?