Invites are now closed to most of the userbase and are only usable by Master user class and above. This means that even if you have invites, you won't be able to use them unless you are Master or above.
Invites are still available through staff sanctioned giveaways in the invite forums of certain private trackers, so if you have any friends that would like to join BTN, send them there.
我那边倒是显示invite(3)不知道是什么意思,反正是发不出来。
还有个东西叫invite codes,我就是前面收到这个注册成功的,不过不知道这个怎么弄。