Hi fellow Prophet folks. I have a Prophet 10 rev4 that's been wonderful the last couple years. I encountered my first head scratcher today.
My DAW is Logic Pro 11.0.1.
The Prophet 10 rev4 is connected via unbalanced, newish Fender guitar cable to the second XLR/line in on a U-Phoria UMC404HD Audio interface.
I noticed today there is nearly 0 impact of the volume knob on the level detected by Logic Pro and heard through my monitor speakers

For example, I currently have the volume knob turned all the way down, and I have a perfectly good audio signal in my DAW. If I turn the volume up, I hear a bit of crackling while turning the knob, but no difference at all in the volume once I have dialed "past" the crackling. Everything sounds identical at a volume of 0 or 10.
The gain is turned all the way down on the U-Phoria channel, and the selector switch is set to LINE. The PAD switch is turned off.
Prophet 10 local control is On.
Is there a mode of operation that would account for the volume knob doing ~nothing while everything else seems to be working perfectly?