D Command--no signal to phones

[oldmanpotter]

I've been using a D-Command for several years. Suddenly I can't get any signal out of the headphone jack. Ordinarily, in the monitor/cues section of the console, I select Phones, choose Main as the source, and hit the ON button and I'm able to hear outputs 1 and 5 (front Left and front Right when configured for the default D-Command surround format L x C x R Ls Rs LFE)

Another engineer has been using the system for a while. Is there a setting somewhere he could have changed? I can hear some low level clicks in the headphones when I change the volume, or change the source that feeds the phones, so it seems there is audio getting to the headphone jack. I also tested the switches using the TEST mode of the UTILITY section--they are all functioning well. I'm also seeing signal on the meters of outputs 1 and 5.

Thanks in advance for any help you can give.