Why can't I hear the timer when Timer+ is in the background?

When Timer+ is in the background, the iOS notification system takes over the responsibility for showing the notifications and playing the alert sounds. Check the following to make sure that you'll hear Timer+ alerts when the iOS notification system takes over.

1. If you recently restored your iPhone or iPad from backup, turn off your device and turn it back on. There is an issue with iOS where apps restored from backup won't receive notifications until you have restarted the device once, even if all of the notification settings are on for that app.
2. Your iPhone or iPad silent/mute switch should be off.The iOS notification system respects the mute switch setting.
3. Your ringer/alert volume level should be high enough. You can adjust the ringer/alert volume level by going to the home screen and pressing the volume buttons. If it doesn't say "Ringer" in the volume display as you change the buttons, go to the iOS Settings app > Sounds, and move the volume slider for "Ringer and Alerts".
4. Notification settings should be enabled for Timer+. To do this, go into Timer+, tap the settings button, and check that the Notification Settings cell is enabled. If it is not, tap on the cell to be taken to the notification settings page to enable sounds for Timer+ notifications.