First check that the volume of your device is not set too low after plugging in the KidJamz. If the volume is set to a high level and you still do not hear any audio, check the USB OTG setting. Some phones, such as many OnePlus models, require USB OTG to be enabled for USB-C audio. On most phones this can be found under Settings -> Other Settings -> OTG Connection. Depending on the phone, USB OTG may need to be enabled again after a set period of time or after phone reboot.