Sometimes we get the following error message, even if nginx is enabled in plesk.

[root@server ~]# /etc/init.d/nginx start
Not starting nginx as it is disabled in config

You can confirm the nginx service is enabled in the server using the following commands.

[root@server ~]# /usr/local/psa/admin/sbin/nginxmng -s
Enabled
[root@server ~]# chkconfig --list | grep nginx
nginx           0:off   1:off   2:on    3:on    4:on    5:on    6:off

Try enablng nginx as root from the terminal will fix the issue.

[root@server ~]# /usr/local/psa/admin/sbin/nginxmng -e
[root@server ~]# /etc/init.d/nginx status
nginx (pid  9873) is running...

Note: The enable/disable operations for the Reverse Proxy Server (Nginx) listed above do not just start and stop the Nginx service. They also switch the web server configuration for all the domains in Plesk (Nginx and Apache combination or just an Apache web server).