Wuhu vouchers not working

In December I logged a complaint again Unilever's Wuhu Rewards for not issuing my Vouchers that I requested. I eventually received the vouchers but when I went to Checkers and ShopRite (I have Shoprite and Checkers vouchers) the vouchers doesn't work. The staff at both stores and their supervisors can't assist me in redeeming these vouchers... I have complained about this and still nothing gets done. Please can someone help me and send me vouchers that can work.