Hi,
Reboot /restart device.
Go to settings >storage>cached data>clear cached data.
Go to settings>storage>apps>google play services>manage space >clear data.
Go to settings>storage>apps>google play store>clear data.
Enable and disable airplane mode.
Switch off and switch on mobile networks.
Switch between 2g,3g,4g.
Enable syncing in google account.
Go to settings scroll down to power manager >tap on this.
Scroll down to battery saver and tap here.
Next screen select the switch off.
Below 5xx versions.
Go to home screen and select power manager app.
Tap on this app.
Disable power saving mode.
Reboot/restart device.
Still problem remains,
Remove sim card insert sim card.
Remove memory card/ SD card( temporarily).
Go to settings>data usage>tap here.
Look at the top of screen.
Tap on the name of the cellular data provider.
below this switch on mobile data.
Tap on the three dot menu at top right.
"Uncheck" in " restrict app background data or
Deselect in " restrict app background data ".
Scroll down to the app(apps) and select app.
Tap on the selected app.
See below the notification" restrict app background data ".
Next to this " uncheck " in the box or
Select the switch off.
Reboot /restart device.
Still problem persists.
Run the device in safe mode( temporarily).
Check for issues causing by any apps.
