Flutter FATAL EXCEPTION error when loading RewardedAds. java.lang.InstantiationError: com.google.android.gms.ads.rewarded.RewardedAd

Question

So I'm using google_mobile_ads plugin version 0.12.1+1 (which is the latest one at this point).

I encountered a strange error and I have tried many things to fix it for the last 3 days without any success.

Please note that it was WORKING and the App is live for more than a few months now, so all the AdMob credentials are correct and I have re-checked it many times.

So I don't know exactly what happened but I have no other place to find solution that I finally post an issue here. I hope someone could help to give me pointers.

The moment rewardedAd.load() is called, the app crashed with error message as follows:

E/AndroidRuntime(27180): FATAL EXCEPTION: main
E/AndroidRuntime(27180): Process: com.me.app, PID: 27180
E/AndroidRuntime(27180): java.lang.InstantiationError: com.google.android.gms.ads.rewarded.RewardedAd
E/AndroidRuntime(27180):    at io.flutter.plugins.googlemobileads.FlutterRewardedAd.createRewardedAd(FlutterRewardedAd.java:154)
E/AndroidRuntime(27180):    at io.flutter.plugins.googlemobileads.FlutterRewardedAd.load(FlutterRewardedAd.java:95)
E/AndroidRuntime(27180):    at io.flutter.plugins.googlemobileads.GoogleMobileAdsPlugin.onMethodCall(GoogleMobileAdsPlugin.java:330)
E/AndroidRuntime(27180):    at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:233)
E/AndroidRuntime(27180):    at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:85)
E/AndroidRuntime(27180):    at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:818)
E/AndroidRuntime(27180):    at android.os.MessageQueue.nativePollOnce(Native Method)
E/AndroidRuntime(27180):    at android.os.MessageQueue.next(MessageQueue.java:336)
E/AndroidRuntime(27180):    at android.os.Looper.loop(Looper.java:197)
E/AndroidRuntime(27180):    at android.app.ActivityThread.main(ActivityThread.java:8167)
E/AndroidRuntime(27180):    at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime(27180):    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
E/AndroidRuntime(27180):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
I/Process (27180): Sending signal. PID: 27180 SIG: 9

In my code:

MobileAds.instance.initialize() is called in main.dart and once the initialization is done the RewardedAd is being initialized like this:

_rewardedAd = RewardedAd(
          adUnitId: AdManager.rewardedAdUnitId,
          listener: AdListener(
            onRewardedAdUserEarnedReward: (RewardedAd ad, RewardItem reward) {
              print('Rewarded Ad successful: $ad reward: $reward');
              // Give reward to user
            },
            onAdLoaded: (Ad ad) {
              setState(() {
                isAdsLoading = false;
              });
            },
            onAdFailedToLoad: (Ad ad, LoadAdError error) {
              print('Error Rewarded Video Ad failed to load: $error');
            },
          ),
          request: AdRequest())
        ..load();

If I remove the ..load() it won't crash but it won't ever load. Once again, this didn't crash before.

What I have done to fix this:

1. I have rechecked all the credentials: App ID and Ad unit Id are all correct.
2. Go through the documentations again to make sure my AndroidManifest.xml are correctly set.
3. Tried both versions 0.12.1+1 (null safety) and 0.11.0+4 (this version is the one used for live version).
4. Tried both debug and release mode.
5. Tried both in Android Virtual Device and real device.
6. There are many others that I don't remember anymore.

Note: The live version is working fine. And I have tried to upload the app to Closed Testing release, but it still crashed.

The flutter run --verbose

It is a long log, so I only include the error part here, but you can read all the full log here

[  +35 ms] E/AndroidRuntime(31757): FATAL EXCEPTION: main
[        ] E/AndroidRuntime(31757): Process: com.me.app, PID: 31757
[        ] E/AndroidRuntime(31757): java.lang.InstantiationError:
com.google.android.gms.ads.rewarded.RewardedAd
[        ] E/AndroidRuntime(31757):     at
io.flutter.plugins.googlemobileads.FlutterRewardedAd.createRewardedAd(FlutterRewardedAd.java:154)
[        ] E/AndroidRuntime(31757):     at
io.flutter.plugins.googlemobileads.FlutterRewardedAd.load(FlutterRewardedAd.java:95)
[        ] E/AndroidRuntime(31757):     at
io.flutter.plugins.googlemobileads.GoogleMobileAdsPlugin.onMethodCall(GoogleMobileAdsPlugin.java:330)
[        ] E/AndroidRuntime(31757):     at
io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:233)
[        ] E/AndroidRuntime(31757):     at
io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:85)
[        ] E/AndroidRuntime(31757):     at
io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:818)
[        ] E/AndroidRuntime(31757):     at android.os.MessageQueue.nativePollOnce(Native Method)
[        ] E/AndroidRuntime(31757):     at android.os.MessageQueue.next(MessageQueue.java:336)
[        ] E/AndroidRuntime(31757):     at android.os.Looper.loop(Looper.java:197)
[        ] E/AndroidRuntime(31757):     at android.app.ActivityThread.main(ActivityThread.java:8167)
[        ] E/AndroidRuntime(31757):     at java.lang.reflect.Method.invoke(Native Method)
[        ] E/AndroidRuntime(31757):     at
com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
[        ] E/AndroidRuntime(31757):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
[  +33 ms] I/Process (31757): Sending signal. PID: 31757 SIG: 9
[ +261 ms] Service protocol connection closed.
[        ] Lost connection to device.
[   +2 ms] executing: /Volumes/ME/Applications/Android/sdk/platform-tools/adb -s 5a53414a33573398 forward
--list
[  +11 ms] Exit code 0 from: /Volumes/ME/Applications/Android/sdk/platform-tools/adb -s 5a53414a33573398
forward --list
[        ] 5a53414a33573398 tcp:59154 tcp:34485
[   +1 ms] executing: /Volumes/ME/Applications/Android/sdk/platform-tools/adb -s 5a53414a33573398 forward
--remove tcp:59154
[  +13 ms] DevFS: Deleting filesystem on the device
(file:///data/user/0/com.me.app/code_cache/my_appCGPZRY/my_app/)
[ +257 ms] Ignored error while cleaning up DevFS: TimeoutException after 0:00:00.250000: Future not completed
[   +3 ms] executing: /Volumes/ME/Applications/Android/sdk/platform-tools/adb -s 5a53414a33573398 forward
--list
[  +16 ms] Exit code 0 from: /Volumes/ME/Applications/Android/sdk/platform-tools/adb -s 5a53414a33573398
forward --list
[   +2 ms] "flutter run" took 140,682ms.
[   +4 ms] Running shutdown hooks
[        ] Shutdown hook priority 4
[   +1 ms] Shutdown hooks complete
[        ] exiting with code 0

The flutter analyze

Analyzing my_app...                                           
No issues found! (ran in 6.1s)

The flutter doctor -v

[✓] Flutter (Channel stable, 2.0.5, on macOS 11.2.2 20D80 darwin-x64, locale en-US)
    • Flutter version 2.0.5 at /Users/ME/development/flutter
    • Framework revision adc687823a (12 days ago), 2021-04-16 09:40:20 -0700
    • Engine revision b09f014e96
    • Dart version 2.12.3
    • Pub download mirror https://pub.flutter-io.cn
    • Flutter download mirror https://storage.flutter-io.cn

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
    • Android SDK at /Volumes/ME/Applications/Android/sdk
    • Platform android-30, build-tools 30.0.2
    • ANDROID_HOME = /Volumes/ME/Applications/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 12.4, Build version 12D4e
    • CocoaPods version 1.10.1

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 4.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
       https://plugins.jetbrains.com/plugin/9212-flutter
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       https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6915495)

[✓] VS Code (version 1.55.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.8.0

[✓] Connected device (3 available)
    • SM G960U1 (mobile)  • 5a5341                         • android-arm64  • Android 10 (API 29)
    • ME iPho (mobile) • b3ebbe938628 • ios            • iOS 14.4.2
    • Chrome (web)        • chrome                                   • web-javascript • Google Chrome
      90.0.4430.85

• No issues found!