Thanks for that information.
Can you try setting the H90 to Receive Omni on?
After that, connect the RJM MIDI output directly to the H90 MIDI input.
Configure the RJM to send some sort of CC message.
Go to parameters mode on the H90, and hold down one of the Quick Knobs to open the parameter mapping menu.
Select CTL Source “Learn” and press the footswitch on the RJM to send a CC message.
Does the H90 recognize this?