If you are still within the 30 days open a not as described case to get a refund. Seller either sends you a return label, or sends the missing bits, or can refund in full. Do Not close case on promises as it cannot be reopened, and promises are easily broken.
Seller could offer a partial refund, which you might be willing to accept, but again do not close case until partial refund received.
It is a waste of time speaking to ebay, you either open a case or if out of time contact your payment provider. Details of money back guarantee are on EVERY listing but only good for 30 days.