This may be happening because I changed cluster compatibility to 4.3 then immediately after changed data center compatibility to 4.3 (before restarting VMs after cluster compatibility change). If this is the case I can't fix by downgrading the data center compatibility to 4.2 as it won't allow me to do so. What can I do to fix this, any VM I restart will break (I am leaving the others running for now, but there are some down that I can't start).
It would seem you ran into the "next" issue that I also ran into. During the upgrade process, the ownership of the disk image of the running VM's gets changed from vdsm.kvm to root.root. (see https://lists.ovirt.org/archives/list/users@ovirt.org/thread/6JFTGJ37KDZQ5KM...) You need to find those disk images and change the ownership back to vdsm.kvm then they will boot again.