Please don't be posting any of the source code in this forum in the future. Are you on the very latest version from the Asset Store?
Now even if it's instantiated at zero, it may be set to another number in the Start method of the Sound Group or Variation, have you checked? Initialization code is fairly complex to get everything to "warm" properly.
Also, are you sure that you aren't attempting to play the "warming" Audio Source while it's busy playing silently? You can turn off warming in Advanced Settings to make sure.
Original Volume should always be set to the Audio Source's volume in edit mode. It it's not, perhaps you adjusted the Audio Source's volume instead of the Volume field on the Variation? You shouldn't touch the Audio Source in Master Audio at all, except for creating custom 3D rolloffs. Let me know if you figure out how it happened.