If you chose a free .onuniverse.com domain:
If the app quits or you exit before publishing your site. Your domain is returned to the database, but it takes 1 - 2 hours to refresh and show up as an option to choose. If you are set on a domain, just wait and try again.
If the domain doesn't show in a couple of hours, feel free to send us a message inside the app or to firstname.lastname@example.org and we'll take a look.
If you chose a custom domain before the app quit:
If you completed the steps to setting up a custom domain before the app closed, the domain is saved to you, but it does not a have a site to attach to. What you'll need to do is create a another Universe site using a free .onuniverse.com domain and then send a message to us with the URL to your new site and your custom domain. What we'll do then is connect it to your domain and you'll be all set.