The Reduce Display Brightness (Plugged In) machine setting should be configured correctly. Specify the period of inactivity before Windows automatically reduces brightness of the display. If you enable this policy setting, you must provide a value, in seconds, indicating how much idle time should elapse before Windows automatically reduces the brightness of the display. Windows will only reduce the brightness of the primary display integrated into the computer. If you disable this policy setting or do not configure it, users can see and change this setting. Fix: (1) GPO: Computer Configuration\Administrative Templates\System\Power Management\Video and Display Settings\Reduce Display Brightness (Plugged In) (2) KEY: HKLM\Software\Policies\Microsoft\Power\PowerSettings\17aaa29b-8b43-4b94-aafe-35f64daaf1ee\ACSettingIndex