Function key + arrow keys (to change volume) not working anymore

Usually, when I try to lower or upper (I don’t now how to say it) volume, I press function (FN) and then either the left or right arrow. Now it stopped working. The only thing I did between the times where it worked and stopped working was search stuff on the web. I didn’t touch settings, terminal, or anything else. This has started at about the same time my laptop stopped sleeping/suspending when I closed the lid (I already fixed that). Anybody know why?