One or more problems was encountered while processing the config files

I don’t have any luck in this. I always have this error when trying to restart the nagios service.

Could not find any host matching ‘printer_groupmain’ (config file ‘/etc/nagios3/conf.d/printers-service.cfg’, starting on line 46)
Error: Could not expand hostgroups and/or hosts specified in service (config file ‘/etc/nagios3/conf.d/printers-service.cfg’, starting on line 46)
Error processing object config files!

I have done everything correctly in command definition
define command{
command_name check_printer
command_line $USER1$/check_snmp_printer -H $HOSTADDRESS -C $ARG1$ -x $ARG2 -w $ARG3$ -c
}

It even works in the /usr/lib/nagios/plugins if i run the command manually, however i can’t run it normally in /etc/nagios3/conf.d.
Appreciate anyone advice on this?

Thanks.