Hia, I am having the same problem as you, and what I found as an alternative is to adjust it from your battery settings. On the bar at the bottom of your laptop page (the one with the time, sound, internet connection, start up, all that on it.) There is this battery with a plug beside it (if it's plugged in, and if it's not plugged in, there won't be a plug) click on that... You should have "Select a power plan" And then there should be "Balanced, Power Saver, High Performance" Ignore all that, underneath it, there should be, "More power options" Click that, and now you should have a new page up, and then click "Change plan settings" Then you get an option where you can change the brightness, remember to save the changes
Good Luck, this is how I do it
Hardware and sound
And then you're at the bit where you gotta click "Change plan setting"
This is the simpler way, if you haven't got that battery thing on the bottom bar.
Hope this helped.