Gift card says already redeemed

Check the suggestions in the link below. It is also possible you are a victim of a scam. Did the card show any sign of being tampered with?

If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card - http://support.apple.com/HT201195

I have to go back to Walmart and get a new one. I plan on activating the new one at the store right after they issue me a valid new card. Apple’s response was sorry, but not our fault. Total bs, clearly from the number of results in the community pages and the fact this has been happening for years (one post was from 2017) they need to update their gift card security. Fix this apple!