RHCOS/MCO don't do much with RHEL7, you need openshift-ansible
Please attache verbose Ansible logs. Was the cluster upgrade to 4.6 complete prior to starting the RHEL7 node upgrades?
The node was stuck during cluster upgrade and openshift ansible was not yet running. Also came across bug https://bugzilla.redhat.com/show_bug.cgi?id=1887607 where currently there is issue with ovn and RHEL nodes. I will close this one as duplicate of above bug. *** This bug has been marked as a duplicate of bug 1887607 ***