It says it right in the message. You aren't welcome on that network. Now as to why, there are a number of possibilities, most (if not all) of which would be explained in the extra lines that were sent from the server, and that you didn't post.
If you want help resolving a problem, we require as much relevant information as possible, which, in this case, are the lines from the server that you didn't include.
Also, please note that a subject line like yours won't bring a faster answer, and may even delay a response since it's too general.
