Why is there no sound when OPPO mobile phone receives information?

There is no sound when the mobile phone receives information, and the elimination method:

1. check whether mute mode is turned on: settings > sound and vibration (sound) > mute (mute mode) > turn off mute;

2. Check whether the mobile phone has turned on the Do Not Disturb mode: Settings > Sound and Vibration >: Do Not Disturb;

3. Has the mobile phone turned off the switch of the notification center: Settings > Notification Center (notification and status bar) > (notification management) > Information > Allow notification \ ringtone;

4. Whether to turn off the notification authority and ringtone in the message: long press the message >; Application > notification management > allow notification > turn on ringtone;

5. Confirm that the volume of the notification bell is not muted: press the volume key >; Click the volume bar to make three points > adjust the volume of the notification;

6. Whether information notification is turned off in mobile phone information settings: Info >; Settings > information notification (ColorOS 3.0 and later systems do not have this setting);

7. Check whether the phone has opened the contact. Don't remind this session: contact > contact details > don't remind this session (ColorOS 3.0 and later systems don't have this setting).