I had this issue a few weeks back, and I fix it, but since I am lazy I didnt note how I did it.
So, what is the issue :
1) In your project you have an audiostream with an audio that works in the game
2) You want to control the volume of this audio, so you add an audio bus
3) Create an audio channel in it, and in the audiostream select the correspondent audio
And then notice that nothing happens and the in game the audio dont change volume.
I dont remember how to fix it ( enable the use of audiobus in the project ), can someone elucidate it ? I had a small memory of having to somehow select the audio channel into the audio file itself, or to enable audiobus to the project somewhere.

    Megalomaniak Hi Mega, I tried to reproduce it today and I was not able to, the only thing I did was to remove and re-add the camera, and for some reason now its working.
    Its not the first time that this happens, I will keep a track and notice here if this happens again, and post a mini project if I can.