Shoprtie/Checkers Voucher invalid

First I received a blank Shoprite Checkers voucher and then the next day I received a voucher but then the voucher is invalid. I thought the branch I went to had an issue so I went to another one and had the same issue. I called the number provided and they take long to answer but eventually did and said must go back to the panel as it is not valid. Sent several emails but no resolution. Service has gone very poor.