my only guess is that you have another ON JOIN event in the same file causing the one you pasted to not trigger.
On a sidenote, I would advise against whois'ing every user that joins your channel.. it makes it extremely easy to flood you off with a mass join in your channel.
It does trigger but it bans anyone i whois. Its only a small chan with about 10 people and no one really mass floods on the network im on so whois eveyone that joins it wont be a problem. This also bans anyone with #A, #b, #c in there chan names
