Help with volume slider for video player

I'm trying to set up a slider that will adjust the volume of the video that is playing. I currently have a slider that adjusts the progress of the video that works just fine. I set my volume slider up the same way (as far as making it slide and the bounds it's contained within) but it fails to actually be draggable. I click on the slider and it disappears from view instead of allowing me to drag it. It's been a while since I've done any AS work and I'm struggling to figure out the problem here as everything appears to be correct. Any help would be greatly appreciated. You can view a demo here. I've attached my source code below.