Can't get external effect box to work with UR44/Cubase 12 Pro

Does anyone know if it is even possible to insert an outboard FX device using an older Steinberg UR44? (I do not have the newer UR44C). My setup is Win10 & Cubase 12 Pro. I’m sending from the UR44/line outputs 3 & 4 to inputs R/L on my Lexicon MX200 and then from the Lexicon outputs R/L back into the UR44 line in 5 & 6. I have all the correct inputs/outputs set up under Audio Connections/External FX. Lexicon shows up in my VST Manager and on the drop down list when I choose to insert or send, neither of which work. All software, firmware and drivers are current. Is it possible that maybe this is beyond the capability of the UR44?

This should work.

If so, it would just work.

Maybe there is something set inside the DspMixFX that prevents the correct signal flow?