It sold 4 days ago and if there has been no further communication looks like your buyer has changed their mind about buying the car.
Annoying as it is you can receive your seller fees back by cancelling the order now, citing Buyer Has Not Paid.
The listing fee will have to be paid, it's the same if you listed your car for sale in your local paper, if it didn't sell, the paper would not refund you your advertising fee.
If you do wish to relist the car, take a look at a Classified ad format. It costs a little mor in listing fees, but when the car sells there's nothing more to pay.
Here's all you need to know about Selling with classified ads: https://www.ebay.co.uk/help/selling/listings/listing-tips/selling-classified-ads?id=4167&st=12&pos=1...
Block the non payer too, from returning to your sales here:
https://www.ebay.co.uk/bmgt/BuyerBlock?
@shannphil