Volume keys on new USB keyboard not working
I purchased a new magic keyboard from Apple last week. The usb is plugged into a belkin thunderbolt express dock hub, which connects to my Macbook Pro (13 inch, mid 2014) running OS X El Capitan version 10.11.6
The letter and number keys work properly, but the volume keys (F10, F11 & F12) do not adjust volume. The F12 key splits the screen to reveal html code for the webpage I'm viewing. Any and all suggestions are welcome.
MacBook Pro (Retina, 13-inch, Mid 2014), OS X El Capitan (10.11.6)