I have an older laptop with a AMD Radeon HD 7400 M Series video card.
Since I installed Windows 10, I kept getting prompts to "Allow Auto Brightness?"
I finally said "OK", but now want to go back to having it under MY CONTROL.
I have been into the Advanced Display Settings, and have created a power plan that allows FULL BRIGHTNESS 100% of the time, and saved it.
It works for awhile, then goes back to sensing the ambient light, and dimming the display! VERY FRUSTRATING.
How can I fix this issue?
I suspect this could be an issue relating to OEM software on your laptop? I would recommend reaching out to the manufacturer and asking them if they have any software installed on your system relating to power management.