The virtual machine could not be started because the hypervisor not running

You may receive the following error when starting a Hyper-V virtual server:

The virtual machine could not be started because the hypervisor is not running.

1. The most common cause is the BIOS does not have virtualization ON. (Enabled)
   
   
2. A more obscure cause is the DEP (Data Execution Prevention) setting.  
   
   On Dell PowerEdge servers, the setting is labeled “Processor Execute Disable”… and should be ENABLED.    
   
   

If you’ve installed Dell OpenManage Server Administrator, the settings are located under System > Main System Chassis > BIOS > Setup (tab):

 

 

OR