STEAM credit code not working?

Hello,

I bought two €50 Steam gift cards from REWE. The first card activated without any problems, but with the second card, an error message appeared stating that the code had already been redeemed. I typed the code in correctly and tried several times. All the cards I've purchased so far have worked without any problems.

I sent all the necessary information, photos of the card, and the purchase receipt to STEAM support. The response I received was that they couldn't send me a replacement and that I should contact the retailer (REWE). For data protection reasons (!!!), support didn't tell me when the code was activated. When I asked again about this and wanted to know how I could prove to the retailer that the code was already active in the store before I purchased the card, support closed my request.

So, aside from the fact that I've never experienced such poor and rude support before, I still don't know what to do. Do you have any ideas or have you encountered the same problem before?

Thanks and greetings

Thorsten