Sorry, I wasn't sure what forum to post this in.

In my System Settings under Power Management, I've set it so that on AC my screen brightness should be at 100% and on battery the brightness should be at 60% and the screen should never turn off. However, when I plug in or unplug my laptop the brightness doesn't change, and on battery my screen turns off after 5 minutes. From searching around it seems like I've somehow accidentally changed my power manager or something, but I don't know how to find out or change it back. Could someone help me figure out how to fix this?