получаю ошибку при отправке push уведомления через свой сервис и через свой скрипт на сайте

FCM сообщения не приходят. (при выполнении метода Send_Notification) Получаю такую ошибку в Logcat при отправке push уведомления через свой сервис и через свой скрипт на сайте:

 <title>Error 400 (Bad Request)!!1</title>

Имеется такой java класс сервиса:

package com.example.my_new_service_fcm;

//package com.protocoderspoint.sendingpushnotificationusingphpcode;

import android.annotation.SuppressLint;
import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.os.Build;
import android.os.IBinder;

import androidx.annotation.NonNull;
import androidx.core.app.NotificationCompat;

import com.google.firebase.messaging.FirebaseMessagingService;
import com.google.firebase.messaging.RemoteMessage;

public class FirebaseCloudMessagingServices extends FirebaseMessagingService {
    public FirebaseCloudMessagingServices() {
    }

    @Override
    public void onMessageReceived(@NonNull RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);

        if (remoteMessage.getNotification() != null) {
            String title = remoteMessage.getNotification().getTitle(); // will hold FCM Title
            String message = remoteMessage.getNotification().getBody(); //will hold FCM message body
            sendNotification(title,message);
        }
    }

    private void sendNotification(String title, String message) {

        NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        String NOTIFICATION_CHANNEL_ID = "admin_channel_1";
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel notificationChannel = getNotificationChannel(NOTIFICATION_CHANNEL_ID);
            notificationManager.createNotificationChannel(notificationChannel);
        }
        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID);
        Intent intent = new Intent(this, MainActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_ONE_SHOT);

        notificationBuilder.setAutoCancel(true)
                .setContentIntent(pendingIntent)
                .setDefaults(Notification.DEFAULT_ALL)
                .setWhen(System.currentTimeMillis())
                .setSmallIcon(R.mipmap.ic_launcher)
                //.setPriority(Notification.PRIORITY_MAX)
                .setContentTitle(title)
                .setContentText(message);
        notificationManager.notify(1, notificationBuilder.build());
    }

    @NonNull
    private static NotificationChannel getNotificationChannel(String NOTIFICATION_CHANNEL_ID) {
        @SuppressLint("WrongConstant") NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "My Notifications", NotificationManager.IMPORTANCE_MAX);
        // Configure the notification channel.
        notificationChannel.setDescription("Sample Channel description");
        notificationChannel.enableLights(true);
        notificationChannel.setLightColor(Color.RED);
        notificationChannel.setVibrationPattern(new long[]{0, 1000, 500, 1000});
        notificationChannel.enableVibration(true);
        return notificationChannel;
    }
}

и майн активити:

package com.example.my_new_service_fcm;

import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.Toast;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import com.google.firebase.analytics.FirebaseAnalytics;
import com.google.firebase.messaging.FirebaseMessaging;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
import com.google.android.material.snackbar.Snackbar;

import androidx.appcompat.app.AppCompatActivity;

import android.view.View;

import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;

import com.example.my_new_service_fcm.databinding.ActivityMainBinding;
import com.google.firebase.messaging.FirebaseMessaging;

import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends AppCompatActivity {

    private AppBarConfiguration appBarConfiguration;
    private ActivityMainBinding binding;

    Spinner spinnerTopic;
    Button subscribe,send_Pushnotification;
    // this link is my server where my php script for push notification exist
    String  URL_NOTI="https://spektr-ekb.ru/push_notification.php";
    String topic;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        binding = ActivityMainBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());

       // setSupportActionBar(binding.toolbar);

      //  NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main);
      //  appBarConfiguration = new AppBarConfiguration.Builder(navController.getGraph()).build();
       // NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration);
        FirebaseMessaging.getInstance().subscribeToTopic("Gadgets");
        spinnerTopic = (Spinner)findViewById(R.id.spinner);
        subscribe=(Button)findViewById(R.id.subscribe);
        send_Pushnotification=(Button)findViewById(R.id.getnotified);
        subscribe.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                topic = spinnerTopic.getSelectedItem().toString();
                System.out.println(topic);
                //subscribing yourself to topic you have selected from spinner
                FirebaseMessaging.getInstance().subscribeToTopic(topic);
                Toast.makeText(MainActivity.this,"Subscribed successfully to:  "+topic,Toast.LENGTH_SHORT).show();
                Toast.makeText(MainActivity.this,"Now just Hit Notify me Button "+topic,Toast.LENGTH_SHORT).show();
            }
        });
        send_Pushnotification.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Send_Notification(topic);

            }
        });


    }



    private void Send_Notification(final String topic)
    {
        StringRequest stringRequest = new StringRequest(Request.Method.POST, URL_NOTI,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        Log.e("farmerorderdataresponse",response);
                        try{
                        } catch (Exception e) {
                            e.printStackTrace();
                            Toast.makeText(getApplicationContext(),"Login Error !1"+e,Toast.LENGTH_LONG).show();
                        }
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(getApplicationContext(),"Login Error !2"+error,Toast.LENGTH_LONG).show();
            }
        })
        {
            @Override
            protected Map<String, String> getParams() {
                Map<String,String> params = new HashMap<>();
                params.put("title","Order Received");
                params.put("body","This is a notification");
                params.put("topic","Gadgets");
                return params;
            }
        };
        RequestQueue requestQueue = Volley.newRequestQueue(getApplicationContext());
        requestQueue.add(stringRequest);
        //Toast.makeText(getApplicationContext(),"Logfgfgfgfg1",Toast.LENGTH_LONG).show();
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public boolean onSupportNavigateUp() {
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_content_main);
        return NavigationUI.navigateUp(navController, appBarConfiguration)
                || super.onSupportNavigateUp();
    }
}

и скрипт на сайте:

<?php
    $user= $_POST['topic'];
    $title = $_POST['title'];
    $body = $_POST['body'];
    $url = "https://fcm.googleapis.com/fcm/send";

    $topic = "/topics/$user";

    //replace serverkey with your firebase console project server key
    $serverKey = "MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQCgFlhGhOWapURi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\ntp4gPk5PnAXAQFC4wGo7/j3S";

    //$body = '$_POST['body']';
  //  $intent_filter=$action;
    $notification = array('title' =>$title , 'body' => $body, 'sound' => 'default', 'badge' => '1');
    $arrayToSend = array('to' => $topic, 'notification' => $notification,'priority'=>'high');
    $json = json_encode($arrayToSend);
    $headers = array();
    $headers[] = 'Content-Type: application/json';
    $headers[] = 'Authorization: key='. $serverKey;
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST,"POST");
    curl_setopt($ch, CURLOPT_POSTFIELDS, $json);
    curl_setopt($ch, CURLOPT_HTTPHEADER,$headers);
    //Send the request
    $response = curl_exec($ch);
    //Close request
    if ($response === FALSE) {
    die('FCM Send Error: ' . curl_error($ch));
    }
    curl_close($ch);
?>

код генерироваол на console.cloud.google.com во вкладке firebase-adminsdk -> keys Скажите, почему возникает ошибка?