Invalid Nandos voucher

Won some vouchers for Nandos but when i got to the store they ALL registered as invalid, the expiry date had not passed but they still all registered as invalid. I then had to forfiet a third working voucher because i could not complete the order without the other vouchers and the order can not be cancelled without nullifying the 3rd voucher. this was incredibly frustrating and embarrassing, i hope you are able to replace all 3 vouchers