I understand that it is a rule to invite outsiders. However, there ARE those who will refuse to invite people. Sometimes this is because they are illegally afk leveling and unable while other times, it is because the new person is just someone they hold a personal grudge against. Either way, it is wrong. If a PK or admin is on at the time, tell them, otherwise, take SS and post them here in admin contact with an explanation.
Having had this done to me countless times, I just got used to it.