To Enable Boost Volume, please follow all these steps:
1. Open The VoicePing Application and Make sure that you are logged in to your account.
2. Tap the 3 dots icon at the upper right corner of the display.
3. Choose "Settings" option.
4. Go to "PLAYBACK OPTIONS" section then enable the "Boost Volume" with a tick by tapping it.
For a clearer guide, please check out this video: