Issue with rewards prepaid mastercard

Hi there, pretty recently cashed in rewards points for a $50 prepaid mastercard. I've used these to pay my bill before but now it's not working. Spoke with customer service at the card company, they said they can't find any problems. I tried to go into the local telus store (since it says redeemable there) and they said they don't accept them. What are my options here, or am I out $50? 😟