Currently running a Denon 3803 receiver and a Kef 2150 sub. The everything was working fine last weekend, but when I tried it today the sub was not producing any sound. The sub, has an auto on/off feature which is activated by the receiver, and it does turn on when the reciver is turned on. I tried running through the speaker level settings 1 by 1, every speaer produces sound, but the sub. Any ideas?