I had similar trouble redeeming a gift card on Amazon. Twice. (thankfully they got resolved upon appeal).

Enough that I am very wary of buying or redeeming gift cards now, especially more than one in a row.

Apparently there's some sort of scam with gift cards, which must affect any platform which allows them, and legit uses often get flagged by automated systems.

If they are so much trouble for Amazon/Apple I wonder why not disallow gift cards, instead of randomly banning users?