@No Sounds?

In the silent mode, it doesn't play audio.  In the Do-Not-Disturb mode, it doesn't play audio and vibrate.

@Disable Sounds

Please turn on the mute switch on your iPhone/iPad/iPod Touch.

@Still No Sounds, No Notifications?

If you cannot get sounds or notifications at all after you turn on notifications for ListTimer in the settings of your iPhone and disable muting and silent mode, please delete ListTimer and install it on the App Store again.