Depending on what VPN you are using, a member may have used the same one in the past. If someone did, and then was banned, that IP will be banned from the forums. If you would like to check the IP address of your VPN then provide it to @Maldesto, he can look it up and see if a banned member has used it in the past. If that is so, there's your problem. If no one has, then it must be a problem with your VPN