Our indexing bot accesses DNS servers once a day to get the IP address of the server hosting the site. If DNS records aren't configured correctly on the site, the bot doesn't get the site's IP address. This means the site can't be indexed and added to search results.
Check the response that the server sends to the indexing bot. If the site is still unavailable, contact your hosting provider to correct the DNS records for your domain. Once the site can be accessed, it may take several days to update the information in Yandex.Webmaster.