When I attach a Chase Bliss Gravitas directly to my midi controller with a cable made to the attached specifications (and no other equipment is attached), the Gravitas executes every midi command sent to it as it should. When I place a Midi Solutions Quadra Thru between the two (as is required to provide midi to the rest of the chain)(and no other equipment is attached), the Gravitas does not respond to any of those same midi messages. If I then connect the MIDI IN of an M-Audio Uno to the Quadra Thru, then the Gravitas executes every midi command sent to it. If I then place the Quadra Thru, the Gravitas, and the Uno into my midi chain the Gravitas does not respond to any MIDI messages. What could be wrong? I've uploaded a video of this test below. Thank you.
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.