I purchased a couple of used AMD Radeon R9 290X cards. One was used for bitcoin mining and had an aftermarket cooler attached. The card is no longer responsive. I realize that the card is, most likely, not a candidate for warranty. Is there an avenue to have the card repaired?
XFX was the only company to have a warranty covering a re-sold card, but they stopped that years ago. You could ask the manufacturer of your card (Sapphire, XFX, etc), but it is likely you're SOL. If you just bought them on eBay then you have purchase protection through them if it's non operational.