You're unfortunately out of time to open an eBay return, their Buyer Protection/Money Back Guarantee is for 30 days.
If the payment was funded by a debit or credit card you have 120 days to issue a chargeback, so are past that timeframe as well.
A section 75 claim can only be issued for credit card payments over £100 when the payment is made direct to a seller, not via an online platform such as eBay, who receive the payment and then pay it to the seller.