Actually, two tips regarding command prompts were provided [EDIT: Okay, three, apparently!], and it’s recommended to run them with Administrator privileges enabled.
To confirm if FxSound driver is installed correctly, go to the directory %PROGRAMFILES%\FxSound LLC\FxSound\Apps and run this command from command prompt,DfxSetupDrv.exe check FxSound Audio Enhancer
The second one:
There were known problems about this with Windows 10 Update (see Method 3).
Method 1:
Start → Run → mmsys.cpl
Method 2:
Uninstall the sound drivers via the Device Manager (without deletion of drivers files). Windows will redetect the sound drivers and enable the missing devices…
Method 3:
Run the command prompt as Administrator:
net localgroup Administrators /add networkservice
Reboot