Esto es lo que viene en el faq de miui, mira a ver si te falta algo:
Q: Why can’t I receive push notification when I quit the Line app or WhatsApp?
A: Normally, push notification is available only when the chatting apps are in use or running in the back-end. If you sign out of the apps or clear the RAM of these apps, it will result in the unavailability of push notification.
If you want to receive push notification, please lock these chatting apps when they clear up, and enable the app auto-start option.
1. Go to “Security” >>“Permission” >> “Auto-start Management” >> add auto-start apps
2. To enable push notification in the status bar, go to “Settings” >> “Notifications” >> “Manage Notifications” >> Open WhatsApp >> “Show in Status Bar” (switch on)
3. Long-tap the Menu key to enter the recent apps back-end. Drag down the app icon to lock it, so it will not be cleared in the following clear-up operation.
