Hdcorea's ip has to be added to the server's hosts file and server's ip has to be added in your hdcorea profile. If the hosts file has the url pointing to the correct ip but server's ip hasnt been added to your profile, you will get 'Can leech only from the registered ip' or a similar error. If hosts file doesn't have hdcorea's ip, you won't connect to hdcorea at all so you don't see any error message is my guess.