The Quadra Thru tries to take power from its MIDI input, so I guess that your controller's MIDI output is not constructed in a way that would allow this. MIDI Solutions sells a
power adapter that might help; also see their
FAQ.
It's also possible that omitting the third signal from the TRS cable is not compatible with the Quadra Thru's output.
I suspect that the most reliable way to run your setup would be some other Thru box that has its own power supply.