• Run the following command:
bcdedit
  • At the end of the list it should show hypervisorlaunchtype as auto. If it is off run this command:
bcdedit /set hypervisorlaunchtype auto
  • Reboot and try to start the VM

Reference:

https://superuser.com/questions/858259/hyper-v-reports-that-the-hypervisor-is-not-running-how-to-start-the-hypervisor