As well as OP’s problems getting dud keys, I would warn that key resellers often contribute to the pickpocketing industry.

Tourist gets lost in Indonesia, kid grabs his wallet. In the time between then and when the tourist calls their bank, the kid buys as many legitimate keys of Game XYZ as he can using the tourist’s credit card, and sells them to G2A.

The bank refunds the fraudulent transactions, but even if the key retailer (eg, Greenmangaming) reports the transactions to the game dev, the dev is often pressured to not revoke the keys since it just leads to poor press off later customers that believe themselves “legitimate” for spending money on the game.

Sites like isthereanydeal.com give more legitimate tracking info and avoid key-sharing sites; the copies sold were obtained directly from publishers. They can also give price history to give you an idea of whether the game will go on sale again soon.