Help, sound not working!

So recently, my laptop has not been allowing me to change the sound volume whether I am using the internal speakers or headphones. It seems to happen when I switch from one to the other.

As you can see, the volume display is grayed and when I try to click on it the slider is gray as well.

Same goes for the window in settings, with the slider also unable to move, stuck at full volume. Also, on occasion, when the sound is working, I cannot change the volume using different methods such as the menu bar, the sound menu in settings, or using the keys on the keyboard. What does work is adjusting the slider in the app that I am using, such as iTunes or in a YouTube video. If anyone knows what I should do, it would be of great help cause this has been annoying me for quite some time. Thanks!