Trace delivery in order: permission, device token, CRM registration, backend send, and device display. Changing Firebase settings randomly can make the original cause harder to identify.
Confirm that notifications are enabled for the app in system settings. Check focus/do-not-disturb settings and Android notification-channel settings. Reopen an app that was force-stopped before repeating the test.
Sign in with the intended customer contact. Confirm that the device-token registration request succeeds against your CRM. A token from a previous installation may no longer identify the current device registration.
Ensure the module’s Firebase project matches the app’s Firebase configuration. Check the backend send result for credential or token rejection. Inspect the exact test audience rather than assuming the device belongs to the selected customer.
For iOS, verify APNs configuration and signing capabilities. For Android, verify the package configuration, notification icon, and channel. Firebase documents platform prerequisites in its FCM setup guide.
Record the platform, app version, test time, foreground/background state, and sanitized send result. Share whether a direct Firebase test reaches the same device while a CRM test does not. Do not include complete device tokens or server credentials in public logs.