Late December 2015, issues with ns2.bluehost.com triggered automatic notice to .is Registrants. The nameserver doesn’t respond to DNS queries.
Bluehost says this is part of a DDoS protection, and that it’s being repaired, and that there is no known ETA of a fix, and that customers should use 3rd party DNS servers and point to their Bluehost IP Address (in the interim or instead).
ISNIC deactivates domains which have a broken DNS configuration after 8 weeks.