First please double-check it is not delivered: was it left in a safe place, or is it with a neighbor?
Then check the tracking or ask the Seller to for these:
- photo of where it was delivered
- signature (if any) of who took delivery
- does delivery postcode match your postcode
If one of these doesn't match your address, then let the Seller know. If they don't refund you then ask eBay to call you so you can explain the situation.
https://www.ebay.co.uk/help/eua?id=5275
Best to call after 9am on Sunday or 8am on Monday.
In the meantime do not open an Item Not Received case because currently tracking shows as delivered, and they will close it in the Seller's favour