『UnityによるARゲーム開発』ーGoogle Places APIの設定に関するご相談

Micheal Lanham著・高橋憲一ほか訳『UnityによるARゲーム開発』（オライリー・ジャパン）という本の内容から質問があります。

この本に沿って、UnityにGoogleMapを読み込み、特定のタイプの場所にマーカーを立てようとしました。
（p200 7章-5 「Google Places APIサービスの設定」）
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しかし、 APIキーを取得してUnityプロジェクト内に設定しましたが、マーカーが表示されません。
作者によるサンプル用完成ファイルをダウンロードしてみましたが、同じようにマーカーが表示されませんでした。
おそらく、この本が出版された2017年当時から、Google Places APIの仕様が変更されたのではないかと思います。

この本についてご存知の方で、マーカーを表示させるためにどのような対応を施せば良いか分かる方がいらっしゃいましたら、ご教授いただければ幸いです。どうぞよろしくお願いいたします。

使用PC：Mac OS Catalina
使用ソフト：Unity Version 2019
使用言語：C#

＊関連があるか明確ではないですが、ゲームをエディター内で実行した際、コンソールで以下のようなエラーが出ました。

NullReferenceException: Object reference not set to an instance of an object

packt.FoodyGO.Services.GPSLocationService.Start () (at Assets/FoodyGo/Scripts/Services/GPSLocationService.cs:55)

ここで、エラーが出ているスクリプトは以下のものです。（当該箇所55行目にコメントを加えました）

【GoogleLocationService.cs】

C#
1using packt.FoodyGo.Utils;
2using packt.FoodyGO.Managers;
3using packt.FoodyGO.Mapping;
4using System.Collections;
5using UnityEngine;
6
7namespace packt.FoodyGO.Services
8{
9    [AddComponentMenu("Services/GPSLocationService")]
10    public class GPSLocationService : Singleton<GPSLocationService>
11    {
12        //Redraw Event
13        public delegate void OnRedrawEvent(GameObject g);
14        public event OnRedrawEvent OnMapRedraw;
15        [Header("GPS Accuracy")]
16        public float DesiredAccuracyInMeters = 10f;
17        public float UpdateAccuracyInMeters = 10f;
18
19        [Header("Map Tile Parameters")]
20        public int MapTileScale;
21        public int MapTileSizePixels;
22        public int MapTileZoomLevel;
23
24        [Header("GPS Simulation Settings")]
25        public bool Simulating;
26        public MapLocation StartCoordinates;        
27        public float Rate = 1f;
28        public Vector2[] SimulationOffsets;
29        private int simulationIndex;
30
31        [Header("Exposed for GPS Debugging Purposes Only")]
32        public bool IsServiceStarted;
33        public float Latitude;
34        public float Longitude;        
35        public float Altitude;
36        public float Accuracy;
37        public double Timestamp;
38        public double PlayerTimestamp;
39        public MapLocation mapCenter;
40        public MapEnvelope mapEnvelope;        
41        public Vector3 mapWorldCenter;
42        public Vector2 mapScale;
43        
44
45		//initialize the object
46        void Start()
47        {
48            print("Starting GPSLocationService");
49
50#if !UNITY_EDITOR
51            StartCoroutine(StartService());
52            Simulating = false;
53#else            
54            StartCoroutine(StartSimulationService());
55            Latitude = StartCoordinates.Latitude;　//エラー（NullReferenceException）
56            Longitude = StartCoordinates.Longitude;
57            Accuracy = 10;
58            Timestamp = 0;
59            CenterMap();
60#endif
61        }
62
63        IEnumerator StartSimulationService()
64        {
65            while (Simulating)
66            {
67                IsServiceStarted = true;
68
69                if (simulationIndex++ >= SimulationOffsets.Length-1)
70                {
71                    simulationIndex = 0;
72                }
73
74                Longitude += SimulationOffsets[simulationIndex].x;
75                Latitude += SimulationOffsets[simulationIndex].y;
76
77                PlayerTimestamp = Epoch.Now;
78
79                yield return new WaitForSeconds(Rate);
80            }
81            IsServiceStarted = false;
82        }
83
84		//StartService is a coroutine, to avoid blocking as the location service is started
85        IEnumerator StartService()
86        {
87            // First, check if user has location service enabled
88            if (!Input.location.isEnabledByUser)
89            {
90                print("location not enabled by user, exiting");
91                yield break;
92            }
93
94            // Start service before querying location            
95            Input.location.Start(DesiredAccuracyInMeters, UpdateAccuracyInMeters);
96
97            // Wait until service initializes
98            int maxWait = 20;
99            while (Input.location.status == LocationServiceStatus.Initializing && maxWait > 0)
100            {
101                yield return new WaitForSeconds(1);
102                maxWait--;
103            }
104
105            // Service didn't initialize in 20 seconds
106            if (maxWait < 1)
107            {
108                print("Timed out");
109                yield break;
110            }
111
112            // Connection has failed
113            if (Input.location.status == LocationServiceStatus.Failed)
114            {
115                print("Unable to determine device location.");
116                yield break;
117            }
118            else
119            {
120                //make sure simulation is disbaled
121                Simulating = false;
122                print("GSPLocationService started");                
123                // Access granted and location value could be retrieved
124                print("Location initialized at: " + Input.location.lastData.latitude + " " + Input.location.lastData.longitude + " " + Input.location.lastData.altitude + " " + Input.location.lastData.horizontalAccuracy + " " + Input.location.lastData.timestamp);
125                CenterMap();
126                IsServiceStarted = true;
127            }
128
129           
130        }
131
132		//called once per frame
133        void Update()
134        {
135            if(Input.location.status == LocationServiceStatus.Running  && IsServiceStarted)
136            {
137                //updates the public values that can be consumed by other game objects
138                Latitude = Input.location.lastData.latitude;
139                Longitude = Input.location.lastData.longitude;
140                Altitude = Input.location.lastData.altitude;
141                Accuracy = Input.location.lastData.horizontalAccuracy;
142                PlayerTimestamp = Input.location.lastData.timestamp;
143                MapLocation loc = new MapLocation(Input.location.lastData.longitude, Input.location.lastData.latitude);
144                if (mapEnvelope.Contains(loc) == false)
145                {
146                    Timestamp = Input.location.lastData.timestamp;
147                    CenterMap();
148                }
149            }
150            else if (Simulating && IsServiceStarted)
151            {                                
152                MapLocation loc = new MapLocation(Longitude, Latitude);
153                if (mapEnvelope.Contains(loc) == false)
154                {
155                    Timestamp = PlayerTimestamp;
156                    CenterMap();
157                }
158            }
159        }
160
161        public void MapRedrawn()
162        {
163            if(OnMapRedraw != null)
164            {
165                OnMapRedraw(this.gameObject);
166            }
167        }
168
169        private void CenterMap()
170        {
171            mapCenter.Latitude = Latitude;
172            mapCenter.Longitude = Longitude;
173            mapWorldCenter.x = GoogleMapUtils.LonToX(mapCenter.Longitude);
174            mapWorldCenter.y = GoogleMapUtils.LatToY(mapCenter.Latitude);
175
176            mapScale.x = GoogleMapUtils.CalculateScaleX(Latitude, MapTileSizePixels, MapTileScale, MapTileZoomLevel);
177            mapScale.y = GoogleMapUtils.CalculateScaleY(Longitude, MapTileSizePixels, MapTileScale, MapTileZoomLevel);
178
179            var lon1 = GoogleMapUtils.adjustLonByPixels(Longitude, -MapTileSizePixels/2, MapTileZoomLevel);
180            var lat1 = GoogleMapUtils.adjustLatByPixels(Latitude, MapTileSizePixels/2, MapTileZoomLevel);
181
182            var lon2 = GoogleMapUtils.adjustLonByPixels(Longitude, MapTileSizePixels/2, MapTileZoomLevel);
183            var lat2 = GoogleMapUtils.adjustLatByPixels(Latitude, -MapTileSizePixels/2, MapTileZoomLevel);
184
185            mapEnvelope = new MapEnvelope(lon1, lat1, lon2, lat2);
186        }
187
188        //called when the object is destroyed
189        void OnDestroy()
190        {
191            if (IsServiceStarted)
192                Input.location.Stop();
193        }
194
195        public MapLocation Location
196        {
197            get
198            {
199                return new MapLocation(Longitude, Latitude);
200            }
201        }
202    }
203}
204