Can't get the sound on my ASUS Monitor MX279 to work


Sep 2, 2016
I have just bought an ASUS MX279 monitor. When I first connected it to my PC, there was sound coming out of the monitor. Then I tried to connect my wireless headphone via bluetooth, the headphone did not have sound. So I tried to disable the sound from my monitor in the Volume Mixer. The headphone then started to work. But when I went back to the Mixer, the icon for the monitor's sound has altogether disappeared. I tried to download the driver and also update it via the device manager, but none of that worked. Any idea how I can fix the problem?

By the way, my OS is Windows 7 Professional.