1. Open "Window Security"
  2. Open "App & Browser control"
  3. Click "Exploit protection settings" at the bottom
  4. Switch to "Program settings" tab
  5. Locate "C:\WINDOWS\System32\vmcompute.exe" in the list and expand it
  6. Click "Edit"
  7. Scroll down to "Code flow guard (CFG)" and uncheck "Override system settings"
  8. Start vmcompute from powershell as administrator net start vmcompute
  9. Restart

Start Hyper-V Manager as administrator

If not working, then

run 'MOFCOMP %SYSTEMROOT%\System32\WindowsVirtualization.V2.mof' from Command Prompt (as administrator) to fix this.....

source: https://github.com/MicrosoftDocs/Virtualization-Documentation/issues/887