If the audio volume was originally normal, then suddenly became quiet and barely audible, please try the following:
On iOS, due to a bug with Bluetooth, the volume may be "locked" at a lower volume than normal, such that even at max volume, you still can't hear anything. To resolve this, please try the following:
1. Swipe up from the bottom of your screen to bring up the Control Center.
2. For volume, drag the slider down to the bottom, then back up to max. This should reset your volume settings for Bluetooth.
Note that on Android, there are separate volume controls for music and calls. You can change them individually by going to your phone's Settings > Audio and sliding the volume for each.
Also, on Android, volume controls for the glasses are separate from the phone. Your phone's audio might be at max volume, while Vue is still at "default" mid-range volume. To resolve this, in the Vue app, change Swipe to control "Volume Up/Down". Then keep swiping forward until you reach max volume on the glasses.