Mark Levinson 380S

I'm sure I'm going to feel like an idiot when I get the answer, but here goes . . .

I just picked up a a 380S Preamp. I have chosen an input for my turntable and named that input PH 4. However, when I set Mode to Monitor, the display reads PH 4 OFF, and I am getting no signal. For the life of me, I can't figure out how to change this to PH 4 ON, or just PH 4. There is no mention of OFF being a setting in the Monitor mode. (FYI, the turntable is feeding into a ML PLS226 Power Supply & 25S Preamp, and the 380S is feeding a ML 333 Amp.)

Any ideas?