Android device cannot receive push notifications when an application is force stopped ("killed")

You may encounter issues with notification delivery caused by Android modifications made by device manufacturers. In most cases these are power-saving settings applied by default: apps are killed when not in use and are not started in the background when a notification arrives. Note that if an app is force stopped from Settings, Android blocks its background delivery entirely until the user launches the app again — this is standard Android behaviour and cannot be worked around by any SDK.

First, check the platform-level settings (all vendors)

• Android 13 and later: the app must be granted the runtime POST_NOTIFICATIONS permission. If the user declined it, no notification is displayed at all. Check Settings → Apps → your app → Notifications.
• Android 12 and later: make sure the app is not in the Restricted battery state and that app hibernation ("Pause app activity if unused" / "Remove permissions if app is unused") is turned off for the app.
• Set battery usage for the app to Unrestricted in Settings → Apps → your app → Battery.

Huawei

• Settings → Battery: disable "Power Saving mode" and "Ultra Power Saving mode".
• Settings → Battery → App launch: turn "Manage automatically" Off for the app and enable all three manual options — "Auto-launch", "Secondary launch" and "Run in background".
• Older EMUI versions: Settings → Battery → set "Close apps after screen lock" to "Don't close"; Settings → Apps → the app → Data usage → allow "Background data".

Xiaomi (MIUI / HyperOS)

• Settings → Apps → Permissions → Autostart: enable it for the app.
• Settings → Battery & performance → choose the app → select "No restrictions".
• In Recents, lock the app so it is not cleared.

Oppo / Realme / OnePlus (ColorOS / OxygenOS)

• Settings → Battery → Battery optimization → choose the app → "Do not optimize".
• Settings → Battery → disable "Freeze when in Background" and "Automatically optimize when an anomaly is detected" for the app.
• Enable Autostart for the app in the phone manager / Startup Manager.

Asus

• Settings → Apps & Notifications: enable notifications for the app.
• Auto-Start Manager: enable it for the app.
• Settings → Apps & Notifications → Special app access: allow the app.

Samsung (One UI)

• Settings → Battery → Background usage limits: make sure the app is not listed under "Sleeping apps" or "Deep sleeping apps", and add it to "Never sleeping apps".
• Settings → Battery: turn off "Power saving" or exclude the app from it.

Sony

• On older Xperia models, STAMINA mode blocks background apps in standby: Settings → Battery → STAMINA mode → add the app to the apps allowed to stay active. On current models, use Settings → Apps → the app → Battery → Unrestricted.

Menu names vary between device models and firmware versions; if an item is not where described, search the device Settings for "battery optimization", "autostart" or "background".