Ebay
Hi if i were you I would ask the seller for a refund on the ground of it not being fit for purpose a motherboard should last longer than 45 days so it doesnt matter about ebay protocol. Then if you get nowhere with the seller raise a dispute with Ebay they nearly always come down on the side of the buyer. MY son sold a vintage games console and after 3 months the buyer said it was no longer working and Ebay refunded his money they didnt even stipulate that he should return the machine. So dont give up give it a go.