you should check te documentation of FCM about this problem. I have this problem now but i resolve modify my request to FCM. Parameters as "priority" help me to solve this problem. To android i used proxy and priority to
mensaje = {
"GCM": json.dumps({
"notification": {
"title": title,
"body": body.strip(),
"icon": "ic_launcher_round",
"android_channel_id": ChannelName,
"proxy":"DENY",
"notification_priority":"PRIORITY_MAX"
},
"data": {
"Alarmas": TextoAlarma,
"Fallas": TextoFalla,
"Superv": TextoSupervision,
"android_channel_id": ChannelName
},
"android": {
"priority":"HIGH"
}
})
}