The LCD Display panel brightness does not change when you use the Fn+F6 or Fn+F7 hotkey combination. This is seen on Latitude systems that launched after March 2019.
This is due to a change in the Default setting of the function keys of newly released Latitude 5000 and 7000 series laptop systems.
The advanced function of these keys is now set to where using the Fn key is not required to change the LCD brightness.
(Fig.1 Fn Keys)
Affected Systems:
There is no hardware problem with any of these systems, they are working as designed. Only the default value of the Function keys has changed.
To change the LCD brightness:
If the Fn Lock is set to disable/inactivate, press F6 or F7 individually to change the brightness (This is the BIOS default setting.)
If the Fn Lock is set to enable/activate, use the Fn+ F6 or Fn +F7 key combination to change the brightness
(Fig.2.1 Fn Lock in the BIOS)
How to enable/activate the Fn Lock:
The Fn+ ESC key combination can be used to enable/activate the Fn lock.
In the BIOS, navigate to POST Behavior > then the Fn Lock Options page and check the box next to the Fn Lock
(Fig.2.2 Fn Lock options in the BIOS)