Serviceが途中で停止している気がするのですが、何が原因でしょうか？どうぞよろしくお願いします。

Serviceで、位置情報を取得して、変更されたら、firebaseに書き込むコードを書いたのですが、
public int onStartCommand(Intent intent, int flags, int startId) {
の中で、startLocation()を呼び出そうとしても呼び出せません。
Serviceが途中で停止している気がするのですが、何が原因でしょうか？

package com.google.android.exoplayer2.demo;

import android.app.Service;
import android.content.Intent;
import android.location.Criteria;
import android.location.LocationManager;
import android.os.Binder;
import android.os.IBinder;
import android.location.LocationListener;
import android.content.pm.PackageManager;
import android.location.Location;
import android.support.v4.app.ActivityCompat;
import android.os.Bundle;
import android.util.Log;
import com.google.android.gms.common.ConnectionResult;
import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.auth.FirebaseAuth;

public class GpsService extends Service implements LocationListener{

    private boolean mResolvingError = false;
    final FirebaseDatabase database = FirebaseDatabase.getInstance();
    private LocationListener sensorEventListener; // onPause()

    public class GpsServiceBinder extends Binder {
        public GpsService getService() {
            return GpsService.this;
        }
    }

    @Override
    public void onCreate() {
        super.onCreate();

        Log.d("onCreate()","呼ばれた");
    }



    public GpsService() {
    }

    //serviceだからいらないかも removeupdatesは必要
//    @Override
//    protected void onPause(){
//        super.onPause();
//        locationManager.removeUpdates(this);
    // mLocationManager.removeUpdates(listener);
//    }

    protected void initLocationService() {
        Log.v("initLocationService()", "呼ばれた");

        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return;
        }

        Criteria criteria = new Criteria();
        criteria.setAccuracy(Criteria.ACCURACY_FINE); //setAccuracyは内部では、https://stackoverflow.com/a/17874592/1709287の用にHorizontalAccuracyの設定に変換されている。
        criteria.setPowerRequirement(Criteria.POWER_HIGH);
        criteria.setAltitudeRequired(false);
        criteria.setSpeedRequired(true);
        criteria.setCostAllowed(true);
        criteria.setBearingRequired(false);
        criteria.setHorizontalAccuracy(Criteria.ACCURACY_HIGH);
        criteria.setVerticalAccuracy(Criteria.ACCURACY_HIGH);

//        locationManager.registerGnssStatusCallback()
//        locationManager.requestLocationUpdates(gpsFreqInMillis, gpsFreqInDistance, criteria, this, null);

        LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
        String bestProvider = locationManager.getBestProvider(criteria, true);
        locationManager.requestLocationUpdates(bestProvider, 6000, 1, this);
    }

            @Override
            public void onLocationChanged(Location location) {

                Log.v("onLocationChanged", "呼ばれた");
                refreshGeoLocation(location);
            }

            //LocationListenerのメソッド
            @Override
            public void onStatusChanged(String provider, int status, Bundle extras) {

            }

            @Override
            public void onProviderEnabled(String provider) {

            }

            @Override
            public void onProviderDisabled(String provider) {

            }


        //ここまで

        // 位置情報のリスナーを取得して登録する
        //sensorEventListener = new GpsLocationListener(sensorValueTextView);


//    public class LocationServiceBinder extends Binder {
//        public com.google.android.exoplayer2.demo.GpsService getService() {
//            return com.google.android.exoplayer2.demo.GpsService.this;
//        }
//    }
    protected void refreshGeoLocation(Location location){
        Log.v("refreshGeoLocation","呼ばれた");
        String user = FirebaseAuth.getInstance().getCurrentUser().getUid();
        DatabaseReference ref = database.getReference().child("users").child(user);
        DatabaseReference latitudeRef = ref.child("latitude");
        DatabaseReference longitudeRef = ref.child("longitude");
        latitudeRef.setValue(location.getLatitude());
        longitudeRef.setValue(location.getLongitude());
    }

    @Override
    public IBinder onBind(Intent intent) {
        Log.v("onBind","呼ばれた");
        throw new UnsupportedOperationException("Not yet implemented");
    }

    private void startLocation() {

        Log.d("StartLocation","呼ばれた");
        initLocationService();
    }

    private void stopLocation() {
        Log.d("stopLocation","呼ばれた");
        //firebase.auth().signOut();これでログアウトはできるが、ログアウトはしない
        database.goOffline();
    }

    //private final LocationListener listener = new LocationListener() {
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d("onStartCommand","呼ばれた");

        String check =intent.getStringExtra("start/stop");

        if(check.equals("start")){
            startLocation();
            Log.d("StartLocation","呼ぶ");
        }else if(check.equals("stop")){
            stopLocation();
            Log.d("StopLocation","呼ぶ");
        }

        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }

    public void movieAdapter(DatabaseReference ref) {
        ChildEventListener childEventListener = new ChildEventListener() {

            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {

            }

            //ここで、firebaseの変化を取得して、Toastを表示する
            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String previousChildName) {
                //```  
Log.v("onChildChanged()","呼ばれた");  
}  

@Override  
public void onChildRemoved(DataSnapshot dataSnapshot) {  
Log.v("onChildRemoved()","呼ばれた");  
}  

@Override  
public void onChildMoved(DataSnapshot dataSnapshot, String s) {  
Log.v("onChildMoved()","呼ばれた");  

}  

@Override  
public void onCancelled(DatabaseError databaseError) {  
Log.v("onCancelled()","呼ばれた");  
}  
};  
ref.addChildEventListener(childEventListener);  
}  
}