Anyone have experience of this or any other stereo DI (not 2 channel, stereo)

Problem is that the damn thing won't output anything and has no indicator to suggest the phantom is on. I have a guitar in the L channel but nothing in the right. Both XLRs are wired to the snake and regardless of whether Phantom was on on the L, or L+R, I get nothing.

Do stereo DIs usually need phantom on both channels? Do you need a cable plugged into both L+R's input for it to work?
Basically, is this normal behaviour for a stereo DI or have I got some slightly defective or just badly designed unit?

PS: manual says nothing about anything.