Did you post to the name and address eBay provided for you on the delivery details for the order? Did it differ from the label? How do you know it failed, did the buyer open a case for item not received? Then, only tracking showing delivery or even attempted delivery would close that case in your favour.
With no access to your account I cannot see what has happened or if any case was opened, all I can suggest is to contact eBay Customer Services as they have full access to your account and to that address provided and can explain what has happened here.
This is the easiest and quickest way to contact eBay Customer Services, for a Call Back option.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
Lines open between 8 a.m. to 10 p.m. on weekdays.
9 a.m. to 6 p.m. on weekends.
I recommend contacting CS very first thing in the morning, when the lines first open, as there's more chance of Dublin answering.
@elainerobins-0
