Was working for me fine yesterday, then not today. MIDI over the MIDI cable was fine. All other MIDI USB controllers I have were fine. Triple checked the settings on the Helix. Using MIDI tester: https://hardwaretester.com/midi in case it was my DAW or its settings. Rebooted the PC and restarted the Helix. None of it did anything to help.
Until I rolled back the latest security patch from yesterday: KB5101650
Now it works fine. (Until the next patch?)