A:Answer I had the same exact issue and it took me a couple days to figure out the problem. That button also acts as a toggle switch - think of it is a hybrid button and light switch - like the ones in your house. If you push up on that button like you do when turning on a light switch, it will turn the subwoofer volume up, and pushing downward (not down), turns the subwoofer volume down. If you push straight down as you would a regular button, it mutes the subwoofer. I hope this helps you out!