I have a Dell Inspiron 5555 that I purchased today from the Microsoft Store. The computer works great, but I've noticed that when I try to change the brightness using the brightness keys (F11 and F12) to adjust the brightness, they don't work. I did get it to brighten up the screen once, but after doing that, I have been unable to make any changes. Has anyone seen this and does anyone know something I can do or try to see if I can make these keys work?
The F keys toggle between Media and normal functions by using the FN key. Try using the FN key with the brightness F key--which is not necessarily F11 or F12. Check your manual. The sun symbols on the Function keys might tell you where the brightness settings are. On my model it is F3 & 4.
You can reverse the toggle settings to make the function you use most the default. The default doesn't use the FN key.
What is the current OS installed on the system? When did the issue start? Were there any recent updates done on the system? Do they work with fn key combination?
As advised by Mary G, are you using the fn key as multimedia keys? Open the Mobility Center and check for the setting.
Update the BIOS - http://dell.to/2a8Jnj7 - restart the system and check.
If issue is not resolved, then restart the system and press f2 on startup to enter BIOS - check if you are able to change the brightness while in BIOS environment.
If the issue is not resolved, then let us know and we shall advise further course of action.
Also, please click my DELL-username and write me a private conversation with the service tag and your contact details(Name and Email) for case records.
Keep us updated.