The tracking record you included (thanks for showing us this, it helps us to advise you) states that it was delivered on 9th February. As eBay's own money back guarantee only lasts for 30 days there is nothing that you can now do through eBay.
If the seller won't reply you may still be able to get help from your payment provider, e.g. credit or debit card issuer. Try this first, but if unsuccessful have a word with Citizens Advice. They will be able to give you more complete advice based on all the circumstances, including the possibility of using the online small claims court system.
