It should be a software setting problem. The settings of each software are different.

Some forums, mailboxes, blogs, and special IDs (such as the mailbox gmail that was previously searched by Google [has been open for registration in February 2007], the dragon clan, Ying Zheng, 3E Empire, etc. in the forum Jianmeng, Deepin, Lilac, and Baidu Index, which we ordinary people don't pay much attention to, etc.), you need a special pass when registering - the invitation code (full name: invitation registration code), the invitation code is equivalent to your Just like entering a registration code when using a software, it has the same function as an invitation in real life. Only when you receive the invitation code can you register an account. When the forum opens invitation registration, the invitation code becomes a necessary condition for registering the forum. If you want to register an ID, you must obtain a valid invitation code. At this time, the normal registration function is generally suspended.

1. The forums of some websites are places for experts to communicate. In order to avoid the registration of some people who are not helpful to improve the overall level of the forum and improve the quality of registered members, an invitation code is set when registering. 2. Some forums have enough members, so they restrict registration; some forums use invitation registration in order to prevent maliciously registered accounts from posting advertisements or malicious spamming, and at the same time hope that members can cherish their accounts. 3. The servers of some forums have limited carrying capacity. In order to reduce the burden on the servers and prevent them from being able to support them, this must not be done. 4. Personally, I think that combining invitation registration and open registration for a period of time is also one of the forum's strategies to attract popularity by playing hard to get.