As everyone know most 6.1+ users were facing charging port issue and once it is fixed from service centre, the device was not getting updates. The main reason for this was the device was not play protect certified. You can check this by following the below step : Open playstore > Settings > Play protect certification, check whether it is mentioned device is certified or device is not certified. So how to fix whose device is not certified. Goto service center and ask them to install lower version os. If possible ask them install 3.51H version or the version whic has July security patch because most of the users who is not receiving update will be on August security patch. Visit the service center and the issue will be solved. My device is now play protect certified and has October security patch installed.