If I assign a button in Panel Builder to "AUDIO" and select any input in vMix, when I click on the button, I see related input audio turn on in the audio mixer and the button tally color changes.
It stays that way until I click the button again and the audio turns off and the tally goes back to original color.
Works perfectly.
If I try the same thing with a bus audio, the audio turns on and off but the tally color doesn't latch the same way as on an input.
Any idea what's going on?

Thanks for the clarification.
I did not see a vBuilder thread.