Control hx stomp through omni port on mc8

Up until yesterday I just had my mc8 controlling my hx stomp and everything was going perfectly. My band uses an MPC live for our live shows and I want to be able to control that with the mc8 as well. The problem is that the hx stomp can’t pass through the sysex messages used to control the MPC. I would like to avoid running to the MPC first, and then back to the hx stomp if at all possible. I thought I could make a custom 1/4" TRS to midi cable and just plug my hx stomp into the omni port on the mc8 and then control the MPC with the midi out on the mc8, but I’m not getting anything on my hx stomp. I’ve tested the cable with a multimeter, so I know that’s not the problem there. I’ve tried all four options for midi out on the mc8 through the editor software, but still nothing on the hx stomp. Am I missing an obvious setting that I need to change on either device?

For HX Stomp, the omniport setting should be MIDI OUT - standard, which is a Type A TRS MIDI output. How did you wire your cable?