If you cannot find the purchase on eBay then you are too late to open a case on eBay, but you can still open an Item Not Received case on PayPal if you paid through them.
You have 180 days (about 6 months) past the date of payment to open a PayPal case there.
Log onto your PayPal account and find your transaction.
https://www.paypal.com/uk/smarthelp/article/what-if-i-did not-receive-my-item-or-it is-not-as-advertised-faq1344
You can escalate the case to PayPal 2 days after opening the case and within 21 days.
Unless the seller has entered tracking showing the item has been delivered PayPal will force a full refund.
Do not forget to escalate the case as this is your last chance to get a refund.
If in the future you do not receive an ordered item, do not leave it so long before opening a case on eBay.
You only have 30 days past the delivery date to open a case in there.
