Problem
On your nagios site you get the following message
NRPE: Command 'UNIVENTION_CUPS' not defined
Investigation
On the specified system you can check:
Which files exist in/etc/nagios/nrpe.univention.d and which permissions do they have?
Do you have modified templates? univention-check-templates
Were all listener modules executed? univention-directory-listener-ctrl modules
Solution
Trigger the listenermodule
univention-directory-listener-ctrl resync nagios-client