Fairlight-CMI

The buyer of my CMI SERIES III is having a couple issues that I was hoping to get some help with.

First, he is unable to play the instrument with the music keyboard.  The keyboard is getting power, as the numeric keypad lights up and functions (the LED didplay works, and the buttons function as they should), but when he plays the keyboard, there is no sound and no indication that the CPU is registering the keys.  He is able to play the Fairlight using a different midi controller keyboard.  

Second, he cannot get audio out of the mono output or the headphones.  When he uses the preview command to audition instruments, he can hear the preview through the headphones but not the mono output.  But he can't hear audio from the mono output or headphones when he plays instruments from a midi keyboard.  

Any ideas on how to troubleshoot these issues?  Thanks.