I am running windows 10, 64bit on my HP Z240 workstation with 2 TB HDD and 16 Gb RAM.   I then enabled  the MS Hyper-V after enabling the BIOS virtual support options.

Starting the virtual machine gave me this error:
<vmachine> failed to start (virtual machine ID xxx)... Virtual machine 'vmachine' could not be started because the hypervisor is not running.  System information shows

  Hyper-V - VM Monitor Mode Extensions    Yes
  Hyper-V - Second Level Address Translation Extensions    Yes
  Hyper-V - Virtualization Enabled in Firmware    Yes
  Hyper-V - Data Execution Protection    Yes

I intend to run a flavour of linux on this VM but could not start it to install the OS.  I must've missed something somewhere so I opted to use the default vm install of windows 10 dev environment. 

Still got the same issue.

Any idea where I've got wrong?

Thanks in advance.