Ensure that your device is not on silent mode. Please check the device's sound settings.
Then, check if you can hear the audio on other apps like Spotify or Youtube.
If you can, that's great! Please go back to the Aritize app, click on the 'Settings' located in the menu bar on the top left corner. Then click on 'Clear cache' and then try scanning the QR code or going back to the channel or experience.