To hear the message tone when you get a message, the message tone needs to be turned on.
Solution: Select message tone
1. Find "Notifications"
Press the message icon.
Press the message icon.
Press the menu icon.
Press Settings.
Press Notifications.
Press the indicator next to "All X notifications" to turn on the function.
Press the indicator next to "Incoming messages" to turn on the function.
Press Incoming messages.
Press Default.
Press Advanced.
Press Sound.
Press Pixel Sounds.
Press the different message tones to hear them.
Once you've found a message tone you like, press Save.
Slide your finger upwards starting from the bottom of the screen to return to the home screen.