A client had a 4 hour power outage today. Though the Hyper-V host, which was connected to a business class UPS, rebooted as it should, none of the VMs came back on line. The Hyper-V management console showed “No virtual machines were found on this server”.
After researching several solutions before simply recreating the virtual machines I restarted the “Hyper-V Virtual Machine Management service”, which was already running. Instantly all VM’s reappeared and started up. Perhaps this may assist others down the road.