Due to recent changes introduced by Windows 10 May 2020 Update to the API used by NoMachine for activating the blanking of the screen, this functionality is no longer available and the remote screen cannot be blanked while a user is connected remotely.

Since Windows API unfortunately doesn't provide anymore the possibility to blank the screen programmatically,
we are working on an alternative solution based on a custom display driver, but it will require more time and at this stage we cannot provide any ETA for that.