onkyo tx-nr616 message "Pwrd Zone2 NonAct"..?

Hi,
my friend has the tx-nr616 with the zone 2 not working. When I press on Zone2 button on the AVR itself and change the volume, the message in the subj appears...

When I press Zone2 button twice on the AVR, it automatically switches to the same input source, but there is no sound.

trying to work the zone2 from the remote doesn't yield any success either.

What can possibly be wrong?

thanks much:)