How to register Nine app to the Unmonitored Apps
If it seems to be restricted the background activity of apps by the system, this is also one of the causes related to the synchronization troubles. To solve this trouble, you have to be eliminated "Nine" in the monitored list by registering Nine to the Unmonitored app list. Please follow the steps below.
1. Open the Settings app on your device and then tap Device maintenance.
2. Tap Battery icon at the bottom-left of the screen.
3. Tap the Unmonitored apps
4. Tap the Add apps menu
5. Add the Nine by tapping Done after marking the checkbox of Nine.
6. You can see Nine registered in the Unmonitored Apps list.