Do you mean Firebase Messaging? If yes: The service is started automatically (by Android/Google FCM service). No extras needed. See the example. Nothing else is needed. How do you send the messages and what kind of messages are you sending (data/Notofication/mixed). Check the energy savings on that device, too. On some devices "unknown apps" (= not in a whitelist like WhatApp) are not allowed to run in the background by default (you can change that manually). I had this on a Huawei P8 which made me mad until I found out.