Some users are faced with the fact that after updating to the latest Windows 10 build (1803 April Update) they can’t change the screen brightness on many laptop models. Brightness control doesn’t work and is stuck at max level at any position of the brightness slider in the settings. Also it is impossible to change the brightness using the keyboard’s function keys.
Almost in 100% of cases, the rollback to the previous Windows 10 build (1709) helps to solve the problem with the display brightness. There are simpler solutions for Windows 10 1803.
If the brightness adjustment issue occurs immediately after upgrading to Windows 10 1803, try to install the last cumulative update KB4284835 (OS Build 17134.112, June 12, 2018). According to information from Microsoft, it fixes the problem with brightness control on laptops with Windows 10 1803.