how do you restart the server? on centos you'd normally use
service openvpn restart
or
/etc/init.d/openvpn restart
if openvpn works from the commandline but not as a service then there's something wrong with your /etc/openvpn files ; there's no need to use 'cd /etc/openvpn' inside an openvpn config file, as long as you use absolute paths to the certificate and key files.
If the openvpn service does not work then check the /var/log/messages file for any warnings/errors (other than 'cannot open config file').
As a final debugging trick you can run
bash -vx /etc/init.d/openvpn restart
and post the output here - it should give a good clue as to what is going wrong here.
