User-created disk-image/machine-image backups to restore Panorama/VM-series firewall instances are not supported across all hypervisors, including private and public cloud platforms. This extends to all functions that allow creating a copy of the disk and the memory state of the instance.
To restore a VM-Series firewall, import a backup of the PAN-OS configuration onto a newly deployed Panorama/VM-series firewall instance from a base image file or from the public cloud marketplace.