It does not work as written to recover a slave with both kvm and openvz.
You have to backup the files indicated in the document. For OpenVZ 7 backup ALL the files in /vz/private including the hidden files but not root.hds.
After having everything backup then reinstall OpenVZ 7 on the slave and Virtualizor. Put the config files back in place. Recover universal.php and reset the database password in the file with the new one.
For KVM prlctl register /vz/vmprivate/UUID (this is not mentioned in the documentation)
Then you can recover from the backup.
For OpenVZ 7 you have to reinstall the OS for each VM from the panel. Then you can recover from the backup. (This is not in the documentation).