Did you have a reserve as there is a large gap between winning bid and underbidder.

Buyers do have 4 days to pay, but if unpaid on day 5 cancel sale using reason buyer has not paid.

Then block this bidder.

Not only time waster, but you will have paid a listing fee, possibly an expensive reserve fee, and a selling fee which will be refunded when you cancel the sale.

I expect the bid is too low to consider making a Second Chance offer, but if relisting, I would suggest using a classified ad.

https://www.ebay.co.uk/help/sr?query=classified+selling&origin=1&aiSummary=true

The advantage is that sale only ends when sold and paid for, if used in this sale, the vehicle would not have ended, but would continue for genuine buyers .

If you did use a reserve, far better to start at a price you would be willing to sell at.