I've just cloned this bug from CFME, becuase there is no error on CFME side. But we need to investigate how is it possible that OVN was improperly configured on RHV side and yet started and make available to communicate with CFME, when the 'client_secret' generation is part of engine-setup, when you enable OVN, so it should always be configured properly.
The workaround was to remove ovirt-provider-ovn, its conf files, and reinstall it.
This is still a bug, but it will be hard to reproduce, unless Nism could elaborate on the changes of engine-setup and ovirt-provider-ovn upgrades along the way.
Nism currently doesn't run V2V as far as I know, so it's not considered V2V blocker.
Nissim, Meni was not involved in this bug. It was filed by Mor who was using your machine. Mor said in comment 4 that you are the only one able to tell what happened on that host.
In other words, please reopen with reproduction steps when this reoccurs.