In the Rackmount forum here; you’ll get more targeted responses in the Stompboxes forum.  Is this using a bass guitar?  If so, and you haven’t done so already, try setting your Source to Bass in System Settings.

Any particular algorithm you’re using for this?  I had the best “power chord” success with H910 / H949 [Modern Type], or the HarModulator.  You can pull off the same 5ths / octaves in Diatonic or QuadraVox., without regard to Key / Scale.  Yes, the latter two will respond better to monophonic input.

It can help to back off the Mix, and favor the 5th over the Octave with Pitch A / Pitch B Mix.  Fine-tune them to be present, yet not fully up front.