So you updated your Windows 10 and now the monitor brightness setting is not working. This issue is found after Windows 10 2004 Update and other major updates. Here are some solutions to fix to Windows 10 brightness issue i.e. unable to change brightness settings.
1. Update driver
This is the basic step. In this step, you need to update your display drivers and graphic cards. Open “Device Manager” > “Display Driver” choose the driver click “Update driver” and then “search automatically for driver”
Do the same for “Monitor”
This will update your exiting drivers to latest available update.
2. Manually select device
Though in most cases device update solves the issue, you might still be unable to change brightness in Windows 10. You need to change the driver of the monitor. Right Click on device under “Monitor” and click update. Choose “Browse my Computer” then “Let me Pick driver from available list”.
Now unclick “Show compatible hardware”.
From the right panel now choose “Generic PNP Monitor” and press next.
You will be able to change brightness right away after a successful installation.