A Second Chance Offer gives you the opportunity to make a sale to bidders who didn’t win your auction.

Are you a buyer who needs information on Second Chance Offers? Read our article on responding to a Second Chance Offer
With a Second Chance Offer, a non-winning bidder gets the chance to buy the item at a price equal to their last bid. You can make Second Chance Offers up to 60 days after an auction ends.

It’s free to make an offer, but if the buyer accepts, you pay a final value fee.

You can use Second Chance Offers when:

Your winning bidder didn’t pay, and you already tried to resolve the issue with them.
Your reserve price wasn’t met.
You have more of the same item available for sale.
In a few eBay Motors and Business & Industrial categories, you can specify the offer price as long as it’s less than or equal to the item’s reserve price.

How to make a Second Chance Offer
It’s easy to make a Second Chance Offer. Here’s how:

Find your listing in either My eBay Selling Activity or Seller Hub.
Select Second Chance Offer from More actions and then Continue.
Select the quantity of items you have to sell, the duration of the offer, and the bidders you want to send offers to. Then select Continue.
We’ll send the bidders you selected an email; it’s their choice whether to accept the offer. Your offer expires if the bidder doesn’t respond within the duration you chose.

Tip
If a winning bidder doesn’t complete a transaction, you can still leave feedback for them as well as for any Second Chance Offer buyers.

Here are some other things to keep in mind when you’re making Second Chance Offers:

If you’re making an offer because the winning bidder didn’t pay, you must cancel the original transaction before you can start the Second Chance Offer.
When you have more of the same item to sell, only make offers to as many buyers as you have items.
You can only send Second Chance Offers to buyers who are willing to see them. Buyers can choose whether to see Second Chance Offers in their communications preferences.

Ref:  https://www.ebay.com/help/selling/listings/selling-auctions/making-second-chance-offers?id=4142