Please perform a push upgrade to this client. This will make sure all components are properly installed. Verify the file /opt/omni/lbin/ob2rman.pl exists on the client and check rpm -qa | grep OB2 if the Oracle package is installed.
Please use the Accept Solution button next to my post and assign a KUDO (thumbs up icon) if this works for you.
Regards,
Sebastian Koehler