Once the end date set for your auction passes, your auction will automatically close. Any items that remain unsold at the end of the auction will be listed in your Items page as Unsold. If you want to keep your auction live after the end date, you can extend it!
Click on the relevant campaign in your dashboard. A green banner may appear at the top of the page.
In the green completion banner, click View items. Alternatively, you can click on your campaign's Auction tab, then on the Items subtab.
Click the three dots [...] on the right side of an Unsold auction item, and select Extend from the list of options.
You'll be taken to the item's details page, where you can make any necessary edits. If you don't have any changes to make, you can scroll to the bottom of the page and click Extend item.
In the window that appears, select your desired new end date for the item. This will automatically extend the entire auction to the new end date for the item.