Flutter Pushy Error: Unhandled Exception: MissingPluginException(No implementation found for method notify on channel me.pushy.sdk.flutter/methods)

Question

I'm using pushy-flutter for push notification service. But my application not able to push notification when the app get killed. It only works well when the app is running or I minimize the application. From the debug console, I can see the apps has received the notification successfully

[+8340 ms] D/Pushy   ( 6919): Received push for package com.afabasia.afab
[        ] D/Pushy   ( 6919): {message=Hello Hell}
[   +8 ms] D/Pushy   ( 6919): Invoking push receiver via reflection: 
me.pushy.sdk.flutter.internal.PushyInternalReceiver
[        ] D/Pushy   ( 6919): Handling notification in Flutter background isolate
[   +4 ms] I/flutter ( 6919): Pushy: _isolate() received notfication
[   +2 ms] I/flutter ( 6919): Pushy notification received: {__json: {"message":"Hello Hell"}, message: Hello Hell}
[        ] I/flutter ( 6919): Received notification: {__json: {"message":"Hello Hell"}, message: Hello Hell}

but when I calling the function Pushy.notifiy(...); , it show me this error

[  +14 ms] E/flutter ( 6919): [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: MissingPluginException(No implementation found for method notify on channel
me.pushy.sdk.flutter/methods)

I have tried the pushy demo project and it works everything well, only in my project, it can't push the notification out when the app is killed. Did I miss out configure something so that my app can't get the Pushy library after the app get killed?

Below are the result of my flutter doctor -v

[√] Flutter (Channel stable, 1.22.1, on Microsoft Windows [Version 10.0.18363.1440], locale en-MY)
    • Flutter version 1.22.1 at C:\Users\zhanm\Desktop\flutter sdk\flutter_1.22.1\flutter
    • Framework revision f30b7f4db9 (6 months ago), 2020-10-08 10:06:30 -0700
    • Engine revision 75bef9f6c8
    • Dart version 2.10.1

[√] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
    • Android SDK at C:\Users\zhanm\AppData\Local\Android\Sdk
    • Platform android-30, build-tools 30.0.2
    • ANDROID_HOME = C:\Users\zhanm\AppData\Local\Android\Sdk
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b04)
    • All Android licenses accepted.

[√] Android Studio (version 3.6)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin version 49.0.1
    • Dart plugin version 192.8052
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b04)

[√] VS Code (version 1.54.3)
    • VS Code at C:\Users\zhanm\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.20.0

[√] Connected device (1 available)`
    • Android SDK built for x86 (mobile) • emulator-5554 • android-x86 • Android 10 (API 29) (emulator)

• No issues found!