Notification sound didn't come back to normal

[jsigeiro]

Hi, guys, God bless you all.
Every night, I put my phone on vibrate mode. During the dawn I receive some notifications normally and when I wake up and put my phone on normal sound mode, the notification sound keeps disabled, so I have to enable it every time. It happens just when I receive a notification on vibrate mode. Could somebody help me with this? Sorry about the english.