As InkPanther and I feel so tired said, bring this issue up with the seller. If they can't give you a refund, then I would definitely start a chargeback through your payment method if you can.
Buying keys from the grey market is dangerous because you don't know how the keys were sourced. If they were bought with stolen credit cards, then the original CC holder will eventually find out and start chargebacks. Then eventually developers lose out on a sale, providing customer service for fake keys, investigating fake keys, and dealing with chargebacks. And then the publisher will revoke the key and you'll lose the game from your library that you thought you paid for.
There are also scummy practices by "social media influencers" or "grassroots promoters" asking for extra keys for themselves and/or their viewers and then going around and reselling them too.
https://arstechnica.com/gaming/2020/05/g2a-confirms-stolen-game-key-sales-pays-40000-to-factorio-devs/
https://arstechnica.com/gaming/2022/08/indie-dev-mounts-successful-sting-operation-against-scammy-steam-curators/
I would always make sure to source keys from GOG, Humble Bundle, and Amazon Prime only so your keys will always be legitimate, devs got paid for their hard work, and your hard earned money doesn't go towards criminals.