You generally need a proof of purchase showing that a product was bought from an authorized reseller in the same country/region as where you're trying to claim the warranty in order for an RMA to be approved, even if the product has not been on the market long enough for any of them to be out of warranty. If you buy used you're extremely unlikely to have this, and dependent on being able to reach the seller, them still having the receipts on hand for an item they no longer own, and them being willing to share them, even though it's no longer their problem.