When you get that error, it means that your user account is not in any of the CUPS administrator groups.
Find the following lines in "/etc/cups/cupsd.conf" :
# Administrator user group...
SystemGroup sys root
and do one of these two things:
- Add your user account to one of the existing "Systemgroup" groups (but I think that adding your user to "sys" or "root" group is a bad idea)
- Add any group your user account belongs to, to that "SystemGroup"line
I always add the "wheel" group to cupsd.conf and make sure I have a user account (not necessarily mine) that is in the "wheel" group so that I can manage my printer configuration.