From looking at the bids, it appears that no-one placed a single bid on the last day of the Auction, and they had plenty of time, as it didn't finish until 21h00.

I agree with Jarl that this is a fair price- no certainty that re-listing would get him a higher price.

If you would like to offer the seller an opportunity, I would let him know that if he can produce evidence within 3 days that the auction was seriously compromised, then you would consider what he shows you, but in the absence of that you expect the seller to complete his contract.