i assume, you have installed OpenACS with the script from
https://openacs.org/xowiki/naviserver-openacsthe 2nd script (install-oacs.sh) installs a systemd file /lib/systemd/system/${oacs_service}.service and/or a upstart script /etc/init/${oacs_service}.conf, where $oacs_service is per default "oacs-5-9". Do you have these files?
if i see correctly, Ubuntu 16.04 has switched to systemd, so the .service file is the preferred path, although one can use Ubuntu 16.04 with upstart as well (see [1]). So this depends on your configuration.
When using systemd, don't forget to run "sudo systemctl daemon-reload". See e.g. [2]. I've updated the wiki page [3] to include these commands.
[1] https://wiki.ubuntu.com/SystemdForUpstartUsers
[2] https://openacs.org/forums/message-view?message_id=5334880
[3] https://openacs.org/xowiki/naviserver-openacs
