I'm not familiar with the EFX controller, so you may need to direct your questions to them.

But, as far as the H9 is concerned, look at the UM under:

[RCV.CTL] – Receive Continuous Control Message

You can follow these instructions to go to the Tuner when you send it the appropriate CC message.

As you point out, you can also do this from H9control. Getting the EFX to send this message is beyond my knowledge – my guess is that is where your problem lies.