The registrar of a domain sets the domain to this status for a number of reasons. You can use Whois to locate your current sponsoring registrar. They will be able to give specific details on why the domain is being held. The domain can not be modified or transferred when in this status. The registrar of the domain is the only one that can remove the REGISTRAR-HOLD status to modify the domain. Also, DNS and zone files are not active for a domain when in this hold status. If you fail to reactivate the domain, then it may go into a Domain Redemption where a large penalty charge will be required to renew the domain.