This question already has an answer here:
FCM not received if App is killed? Even not showing in system tray. Working fine in foreground/background state. I have used the below payload.
{
"to":"dV_9vNhqkXE:....",
"notification": {
"title":"1",
"body" : "11",
"icon" : "ic_about"
},
"data": {
"type":"11",
"month":"3333",
"title":"2222"
}
}
This link will help you understand more about the state of activities in their foreground and background. It basically says that you wont receive any notification if you have force closed your app, because "When the app is closed forcelly by the user : notifications don't arrive". So, did you force close the app ?