On LS9-32, your MONO master fader is the fader 32 in the Master layer.
But, on LS9-16, there's no MONO master fader assigned in any layer as the factory default.
1. Please press the [SETUP] key repeatedly to access the USER SETUP screen.
2 Move the cursor to the CUSTOM FADER LAYER popup button in the screen, and press the [ENTER] key. The CUSTOM FADER LAYER popup window will appear.
3. Move the cursor to one of the faders and select "MONO" with the parameter wheel, then press the [ENTER] to set.
Master faders for Matrix are not assigned to any layer neither. If you would like to have them on the console, please assign them to the faders in the same way.