If you have opened a case for item not received, the seller has 3 days to accept it, and only if they enter a valid tracking number will the case close in their favour.
On day 4, if there is no refund, no action from the seller, then escalate the case, eBay step in and force the refund.
If a tracking number is entered, closes the case and you can prove the item was not sent to the delivery address you have registered on your eBay account, ( have you checked this, have you recently moved and forgotten to change this vital detail ? ), then contact eBay Customer Services they have full access to your account and can see if the address / postcode the seller used , is not the one you have on your delivery address in eBay.
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 8 a.m. - 10 p.m. on weekdays
9 a.m. - 6 p.m. on weekends.
Automated agents will be available on chat outside of the above hours.
I recommend contacting CS first thing in the morning as there's more chance of Dublin answering.
@o5veter