I found that there is a user blocked in the backend, showing the operating IP as the server's IP, not the IP of any of our administrators. is there some rule that automatically blocks the user?
TL;DR
Users cannot be blocked automatically by any rule. It is possible for users to block themselves, but there is no rule that automatically blocks them. Additionally, the fact that an anonymous user is being shown as blocked with the server's IP is strange and may require further investigation.