Only 70% users get firebase notification Received

Question

I am using Latest firebase "firebase-bom:29.0.3" SDK And I am sending notification by Topic and also tried by token array in previous code

Android Code

Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);

NotificationCompat.Builder notificationBuilder =new NotificationCompat.Builder(this, channelId)

                    .setSmallIcon(R.drawable.ic_notification)
                    .setContentTitle(title)
                    .setContentText(messageBody)
                    .setAutoCancel(true)
                    .setSound(defaultSoundUri)
                    .setPriority(NotificationCompat.PRIORITY_HIGH)
                    .setContentIntent(pendingIntent);

NotificationManagerCompat notificationManager = NotificationManagerCompat.from(getApplicationContext());

// Since android Oreo notification channel is needed. if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) { NotificationChannel channel = new NotificationChannel(channelId, channelId, NotificationManager.IMPORTANCE_DEFAULT); notificationManager.createNotificationChannel(channel); }

notificationManager.notify(id, notificationBuilder.build());

Php CODE

 $msg = array(
            'title'  => $title,
            'body'  => $message,
            'text'  => $message,
            'sound' => 'default',
            'badge' => $badge,
            'id' => $id,
            'type' => $idType,
            'timestamp' => time()
        );
          
        $fields = array('to' =>'/topics/global', 'notification' => $msg, 'data' => $msg); 

        if(!empty($fields)){
            $headers = array('Authorization: key=' . env('FIREBASE_FCM_API_KEY'),'Content-Type: application/json');
            #Send Reponse To FireBase Server
            $ch = curl_init();
            curl_setopt($ch, CURLOPT_URL, 'https://fcm.googleapis.com/fcm/send');
            curl_setopt($ch, CURLOPT_POST, true);
            curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
            curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
            curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
            curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));
            $result = curl_exec($ch);
            return $result;
        }
        else{
            return 0;
        }