What was the latest estimated delivery date stated in the listing? Bear in mind that many deliveries are delayed during the pandemic, so it's fair to allow a few more days before taking any action.
If it's significantly overdue you can open a case under eBay's money back guarantee, through the resolution centre (see foot of page). To qualify, you must have paid through eBay's checkout, using PayPal or PayPal Credit, a credit card, debit card, Google Pay or Apple Pay.
A case must be opened within 30 days after the latest estimated delivery date. The seller is allowed 3 business days in which to respond. After that, the option will appear for you to escalate the case, if necessary, for eBay to step in and help. This option remains available for 21 days from the date the case was opened.
If the seller doesn’t respond with a solution, or you're not happy with their response, escalate it. The seller will be required to provide eBay with tracking evidence of successful delivery. If they can't, eBay will enforce a full refund. Follow any instructions and time limits carefully, and don't agree to close the case until you have received your refund.
To read the full terms and conditions of eBay's money back guarantee, see: http://pages.ebay.co.uk/help/policies/money-back-guarantee.html
