This type of error usually occurs when there is a problem with the Flutter and Kotlin dependencies in your Android project. In this case, the FlutterFragmentActivity class cannot be resolved correctly.

-Review your dependencies: Make sure that the required dependencies are included in your app's build.gradle file in the dependencies section

implementation 'io.flutter:flutter_embedding_debug:<flutter_version>'

-Update Flutter and Gradle

• Check your project settings on Android: Make sure your project is properly configured to work with Flutter. Open the MainActivity.kt file and verify that the import and class are correct

  package com.app.myproject

import io.flutter.embedding.android.FlutterFragmentActivity

class MainActivity: FlutterFragmentActivity() { }