The Virtual Machine could not be started because the hypervisor is not running

If you get this error and expand the details you will see 3 possible causes for the error.

The first 2 are obvious and should be checked in the BIOS.

The 3rd option could have happened if you have edit your Boot Configuration Data Store or have reimaged your computer and then recreated the BCD for dual boot.

The solution is simple:

bcdedit /set hypervisorlaunchtype auto