Redeem code isn't working

Hello! I don't know if this is the right place to ask, if not you can point me to right one. But I have a problem with Sims 4 Get to work expansion pack. You see I bought the physical copy on the market. Seller seemed like a collector and sold games second hand but copy was still in plastic and seemingly unused so I bought it. But when I tried to redeem code it says the code has already been used. My guesses are that someone used the code and after that the copy has been replasticed and sold again. I don't know if this spesific seller was behind that or did he get the copy somewhere else. Or maybe the code is faulty? So I was wondering is there something I or EA could do about it? Is there possibility to get a new code or something? I payed almost full price on that thing, it would be kinda bummer if I don't get what I payed for. I have both the copy and the code right here so just ask if you need something.

Reaching out for the seller is sadly very hard since it was a market. They didn't do receipts and I don't have his contact info. So I thought to ask here as the last resort.