Acer Aspire V5-431P-4653 :: Cannot Adjust Screen Brightness Running Windows 8.1

I am having an issue with my Acer Aspire V5-431P-4653 running Windows 8.1, namely, I cannot adjust the screen brightness at all. It seems to arbitrarily select a brightness level upon start up and from that point I cannot change it via the Fn and directional keys or through the control panel power settings. I have owned the laptop for a year and a half and this problem began roughly a week ago. 
 
Of note, when I attempt to use the Fn and directional keys the brightness icon that pops up stays at the frozen brightness level - it does not move at all. In contrast, when I open the power settings and attempte to change the brightness from there, the brightness slider will move wherever I drag it, but the screen's brightness itself does not change. At startup the screen's brightness may be at full, minimum or somewhere in between - but regardless it will not adjust.