Using GoogleVR 1.50.0, whenever the app is switched into Cardboard mode the volume controls are disabled due to the android volume bar not showing in Stereo. I get that reasoning, but is there any way to override the disabled volume controls and allow the buttons to change the volume without showing the android volume bar or showing a custom volume bar within Unity?
Nevermind, this appears to be a bug within Unity which was fixed in versions 5.6.3f1 and 2017.1.1f1.
Found this closed thread on GoogleVR’s github which cleared that up.