The buttons on the front panel are toggle on/off switch. 

Power button:  Red means Standby and Green means power on.  No Light means AC power switch off.

Channel 1 ~ 8, Red light means the source is set to XLR and Green means the source is set to RCA.  No Light means the channel is turn off.

The light in between 1 & 2, 3 & 4, 5 & 6, and 7 & 8 are Mono indicators.  Red light also means the source is set to XLR and Green means the source is set to RCA.  No Light means the channel is turn off.  The mono channel can be toggled on/off with channel 2, 4, 6, & 8. 

Please make sure to press the buttons to turn on the channels.  Since our stereo lights are very small LED on the button top, so it might be easy to miss if its put inside the rack.