To receive audible notifications on your smart device, your smart device should not be in Do Not Disturb mode, and notifications need to be enabled for the Sense-U App in Settings->Notifications->Sense-U Baby. For Android devices, turn on and increase Media Volume in Settings->Sounds & Vibration->Volume.
If you have any further questions, feel free to submit a request here, contact us via in-app Feedback (from the Sense-U App->Setup->Help->Feedback) for expedited diagnose, or email us at support@sense-u.com