Poor service from FNB E-bucks

I bought an E-bucks voucher for Sportmans Warehouse for my wife. The voucher is not working. It says it is invalid. The voucher was tried at two stores already (Atterbury - 7 May 2022) and (Stoneridge - 16 May 2022). I have been calling the E-Bucks call centre three times already, but no one can assist me. I'm really getting frustrated now.