So I have read a lot of diffrent ways to solve this problem and I have searched for hours looking for a solution, yet nothing i've tried has worked for me. Whenever i press the fn key and try to adjust brightness then it does't, it does pop up the slider at the corner but it only moves upwards and downwards only one level yet the brightness wont change even that much. I only found one other person that had this problem and he got it solved, but he had an Asus laptop and he got it fixed with some Asus drivers but i have a Dell Vostro laptop. One of the biggest suggestions i have found that has worked for people has been to install some older display drivers, but that hasn't worked for me either.