There are chances the adaptive brightness feature prevents to change screen brightness. Nowadays most displays or laptops equipped with an ambient light sensor, And the adaptive brightness feature in Windows 10 automatically adjusts the screen brightness to match the ambient light.

Once done restart your PC to apply them and check the status of Screen brightness settings Turn off adaptive brightness.

This will start download windows updates from the Microsoft server, and Update the display driver as well.

Click on Update & security then hit the check for updates button,.

Installing the latest windows updates fix previous problems as well, Lets install available windows updates first. Microsoft regularly releases windows updates with the latest bug fix and security improvements.

Press one of them or probably have to hold down the Fn key while using these keys and check if you are able to change the screen brightness.

If you’re a laptop user, Look for a sun symbol on your keyboard these keys are function keys on the laptop that used to adjust (Up or down) screen brightness on your laptop. This will restart all drivers including the Graphics driver and fix if a temporary glitch prevents screen brightness function normally. If this is the very first time, you are unable to adjust the display brightness with dedicated keys on your keyboard, or brightness slider we recommend reboot your PC.

Brightness setting not working