How exactly do people fail? Here are some debugging tools:
Can their computers access the server at all? Test with "ping".
Are their browser requests reaching the server? Test by checking the access log on the server. For example, you can tail the access log (tail -f /web/service0/log/access.log), look at the last line, then go make a request from another computer, then look at the last line again. If it didn't change, they aren't reaching the server.
Is there a firewall in the way? Is there a firewall on the server that blocks remote access?