i am so nubie about kamailio

i follow the tutorial kamailio skype in one hour.

i install on vps and give the public ip

before i change the kamailio.cfg from the tutorial i run ps -fC kamailio have result and can register.but when i change kamailio.cfg from the tutorial run ps -fC kamailio no result and can't register.

any help please need private sip server urgently

thanks