It looks like a scratch-off code like on Netflix gift cards. Once you scratched it off there won't be a refund available would be my guess just like any other gift card and many digital purchases.
So my guess would be Amazon doesn't take returns on giftcards in the first place.
Look at the hundreds of people online who bought Battlefield 2042 from Amazon. They ship a CD case with a slip of paper inside which has a code.
Hundreds of people tried to redeem codes that had already been used.
This happens to every code-consumption-based retailer. Thankfully Amazon still eats the cost of "doing business" currently.