Fix

Assets/Plugins/Android/AndroidManifest.xml

@@ -2,12 +2,13 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.unity3d.player" android:installLocation="preferExternal" android:versionCode="1" android:versionName="1.0">
   <supports-screens android:smallScreens="true" android:normalScreens="true" android:largeScreens="true" android:xlargeScreens="true" android:anyDensity="true" />
   <application android:theme="@android:style/Theme.NoTitleBar.Fullscreen" android:icon="@drawable/app_icon" android:label="@string/app_name" android:debuggable="true">
-    <activity android:name="com.unity3d.player.UnityPlayerActivity" android:label="@string/app_name">
+    <activity android:name="com.google.firebase.MessagingUnityPlayerActivity" android:label="@string/app_name" android:theme="@style/BaseUnityGameActivityTheme" android:exported="true">
       <intent-filter>
         <action android:name="android.intent.action.MAIN" />
         <category android:name="android.intent.category.LAUNCHER" />
       </intent-filter>
       <meta-data android:name="unityplayer.UnityActivity" android:value="true" />
+      <meta-data android:name="android.app.lib_name" android:value="game" />
     </activity>
     <activity android:name="com.facebook.unity.FBUnityLoginActivity" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" android:theme="@android:style/Theme.Translucent.NoTitleBar.Fullscreen" />
     <activity android:name="com.facebook.unity.FBUnityDialogsActivity" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" android:theme="@android:style/Theme.Translucent.NoTitleBar.Fullscreen" />

Assets/Plugins/Android/FirebaseCrashlytics.androidlib/res/values/crashlytics_build_id.xml

@@ -1 +1 @@
-<?xml version="1.0" encoding="utf-8"?><resources><string name="com.crashlytics.android.build_id" translatable="false">b1198bcb-9e68-42ca-afdc-de38c0753861</string></resources>
+<?xml version="1.0" encoding="utf-8"?><resources><string name="com.crashlytics.android.build_id" translatable="false">0a4c6c8f-8290-4f0a-8af5-899267e3f184</string></resources>

Assets/Plugins/Android/MessagingUnityPlayerActivity.java

@@ -0,0 +1,82 @@
+/*
+ * This file is generated by the FirebaseMessagingActivityGenerator script.
+ * Refer to that script for more information.
+ */
+
+package com.google.firebase;
+
+import android.content.Intent;
+import android.os.Bundle;
+import com.google.firebase.messaging.MessageForwardingService;
+import com.unity3d.player.UnityPlayerGameActivity;
+
+/**
+ * MessagingUnityPlayerActivity is a UnityPlayerGameActivity that updates its intent when new intents
+ * are sent to it.
+ *
+ * This is a workaround for a known issue that prevents Firebase Cloud Messaging from responding to
+ * data payloads when both a data and notification payload are sent to the app while it is in the
+ * background.
+ */
+public class MessagingUnityPlayerActivity extends UnityPlayerGameActivity {
+  // The key in the intent's extras that maps to the incoming message's message ID. Only sent by
+  // the server, GmsCore sends EXTRA_MESSAGE_ID_KEY below. Server can't send that as it would get
+  // stripped by the client.
+  private static final String EXTRA_MESSAGE_ID_KEY_SERVER = "message_id";
+
+  // An alternate key value in the intent's extras that also maps to the incoming message's message
+  // ID. Used by upstream, and set by GmsCore.
+  private static final String EXTRA_MESSAGE_ID_KEY = "google.message_id";
+
+  // The key in the intent's extras that maps to the incoming message's sender value.
+  private static final String EXTRA_FROM = "google.message_id";
+
+  /**
+   * Workaround for when a message is sent containing both a Data and Notification payload.
+   *
+   * <p>When the app is in the background, if a message with both a data and notification payload is
+   * received the data payload is stored on the Intent passed to onNewIntent. By default, that
+   * intent does not get set as the Intent that started the app, so when the app comes back online
+   * it doesn't see a new FCM message to respond to. As a workaround, we override onNewIntent so
+   * that it sends the intent to the MessageForwardingService which forwards the message to the
+   * FirebaseMessagingService which in turn sends the message to the application.
+   */
+  @Override
+  protected void onNewIntent(Intent intent) {
+    super.onNewIntent(intent);
+
+    // If we do not have a 'from' field this intent was not a message and should not be handled. It
+    // probably means this intent was fired by tapping on the app icon.
+    Bundle extras = intent.getExtras();
+    if (extras == null) {
+      return;
+    }
+    String from = extras.getString(EXTRA_FROM);
+    String messageId = extras.getString(EXTRA_MESSAGE_ID_KEY);
+    if (messageId == null) {
+      messageId = extras.getString(EXTRA_MESSAGE_ID_KEY_SERVER);
+    }
+    if (from != null && messageId != null) {
+      Intent message = new Intent(this, MessageForwardingService.class);
+      message.setAction(MessageForwardingService.ACTION_REMOTE_INTENT);
+      message.putExtras(intent);
+      message.setData(intent.getData());
+      MessageForwardingService.enqueueWork(this, message);
+    }
+    setIntent(intent);
+  }
+
+  /**
+   * Dispose of the mUnityPlayer when restarting the app.
+   *
+   * <p>This ensures that when the app starts up again it does not start with stale data.
+   */
+  @Override
+  protected void onCreate(Bundle savedInstanceState) {
+    if (mUnityPlayer != null) {
+      mUnityPlayer.destroy();
+      mUnityPlayer = null;
+    }
+    super.onCreate(savedInstanceState);
+  }
+}

Assets/Plugins/Android/MessagingUnityPlayerActivity.java.meta

@@ -0,0 +1,28 @@
+fileFormatVersion: 2
+guid: e79bd7233f70e4addb0fced7e984ef06
+labels:
+- FirebaseMessagingActivityGenerated
+PluginImporter:
+  externalObjects: {}
+  serializedVersion: 3
+  iconMap: {}
+  executionOrder: {}
+  defineConstraints: []
+  isPreloaded: 0
+  isOverridable: 0
+  isExplicitlyReferenced: 0
+  validateReferences: 1
+  platformData:
+    Android:
+      enabled: 1
+      settings: {}
+    Any:
+      enabled: 0
+      settings: {}
+    Editor:
+      enabled: 0
+      settings:
+        DefaultValueInitialized: true
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: