Discovery active rewards ****

I had a terrible experience with Vitality rewards, I saved up my points and used it got a Nandos R100 voucher, tonight my Wife and I went to Nandos to redeem the voucher and pay for our meal when the app says "cannot retrieve information, please try again later, I sat at the teller trying to redeem the information when eventually I had to pay in cash and not the voucher as it could not be accessed. This is terrible service, as this was very embarrassing and left me red faced. What is the point of getting these rewards if you can't use themm