if you use -v3 you will see the reason ..
66-enable: info: Read service file of : cupsd at: /etc/66/service/
66-enable: info: Parsing cupsd service...
66-enable: warning: unable to use cupsd service: permission denied
66-enable: warning: unable to keep common
66-enable: warning: unable to keep information of: cupsd service
66-enable: fatal: invalid service file: /etc/66/service/cupsd
unable to use cupsd service: permission denied < that's the reason
if you look at the service file declaration you will see
@ user = ( root )
Only root have the permission to use the service.
Now if you try as normal user
$ cupsd
you will get
zsh: permission non accordée: cupsd
So, the daemon need root privileges to be launched