LeeJ07

You're correct, RD. 

3DS is region locked for 3DS games, but DS games from all regions work on it just fine. I actually already have two other Euro DS games that work perfectly. 

In this case, I'm just consistently getting a message that says "No Game Card Inserted" every single time I load this new game. I'm familiar with the message because it actually pops up frequently when a card is not seated against the contacts properly, but usually removing and then re-inserting the game fixes it. Sometimes a game has dirty contacts, but I've already tried cleaning the contacts three times, too, and that's not doing it, either.

I've literally never found a DS game that's completely dead before, so I'm kind of at a loss. It's not showing any signs of abuse or damage, so I literally cannot imagine what's wrong with it. I'm about to crack it open, though, and look inside.

Cracked it open, interior is clean. 

I can only assume that the main chip is bad, which is such a vanishingly rare thing, but eh. As far as I can tell, it can't be fixed.

If you can't work out a resolution with the seller directly, you should use ebay's process and report that the product is defective. You should be able to get a full refund via ebay.