You can't do anything through Ebay and you are too late to raise a case with your payment provider.
Ebay expect you to open a case within 30 days of receipt and most banks give you 120 days to start a chargeback.
You do need to check your purchases promptly otherwise, as you have found, you lose the protection offered by the Money Back Guarantee.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
