Add or Remove Display brightness from Power Options in Windows  

Brink said:

Hey mate,
You might see if you have adaptive brightness enabled, and disable it if so.
Enable or Disable Adaptive Brightness in Windows 10
In addition, the screen will dim a bit by default right before the display is set to turn off.

Hello Brink, I don't have either setting.

Brink said:

Does it dim after a specific time or action?

Starts dimming immediately but does it gradually almost to the point that you can't see it change.

Brink said:

If you haven't already, you might check to see if you have a newer graphics driver available, or roll back to an older one to rule out an issue with the graphics driver.

There is updated drivers for display and mouse pad but I pass on both. The display driver removes the ability to run "preserve aspect ratio" and the mouse pad driver removes the option to have the pad disabled if a mouse is plugged in.

I will suffer with the display dimming since I run it at 70% normally any way and that leaves me room to increase the brightness to a desired level.

Brink said:

You might also check to see if Night Light may have been turned on by mistake.
Turn On or Off Night Light in Windows 10

Night Light is off also.