systemctl status openvpn@server.service"?

In regard to this error; sudo systemctl start openvpn@server Job for openvpn@server.service failed because the control process exited with error code. See “systemctl status openvpn@server.service” and “journalctl -xe” for details.

Edit: /etc/openvpn/server.conf Then comment on if uncommented: ‘ifconfig-push’

Check the logs to guide on errors generated by the system. Use this command; tail -50 /var/log/syslog

Sorry to see that your question hasn’t received an answer yet. Unfortunately, after this much time, it is unlikely that an answer for this specific question will be provided. For people still landing here via search, I would suggest starting by looking at the service’s logs. The commands sudo systemctl status openvpn@server.service and sudo journalctl -u openvpn@server.service should help you view the logs.