Do you use a service such as Cloudflare or Incapsula? Try disabling it.
It's possible you have their IP addresses blocked in the vBulletin AdminCP > Settings > Options > User Banning Options.
If you completely can not access the forum because of that, open /includes/functions.php, look for the "verify_ip_ban" function and remove everything inside of it. If that also doesn't work then it has to be a plugin/script causing this.
|