May I ask what happened to the forum
My account cannot be logged in and I can only register and log in again with my previous ID
There was a significant upgrade to the system (see this link) and many (if not all) users had to reset their passwords.
For spam reasons, multiple accounts with the same IP and the same cookie on the browser are disabled… or not? 
Give me a valid reason to have multiple forum accounts, except that you’ve ruined your reputation and pretend to be another person…
normal operation
Because several people discovered abnormalities in the forum and re registered through the same PC browser for operation
Currently, it has been found that another account has been disabled, which is very hurtful to users
Spam on the forum is not welcome, don't you understand that?
Having multiple accounts doesn't make sense, so stop ruining your reputation every time and use only one.
What you are describing is an anomaly.
You can’t spam your signature, you can’t spam your profile description, you can’t put hidden spam links,
you can’t write spam messages when you first sign up, you can’t post unless you’re authorized…
It’s not an anomaly, it’s how the forum works…
But what are you doing, do you manage a cooperative of spammer users on the various forums?
On how many sites does the cooperative spam?