ListView.builder is not scrolling in flutter

Instead of using ListView.Builderinside CustomScrollView. It is always better to use Slivers. Therefore, instead of wrapping ListView.builder with SliverToBoxAdapter, use SliverList. Here is the detail code I have refactored below for you. Or you can directly visit this link where you can play with the refactored code.

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.light(),
      home: const DashboardScreen(),
      debugShowCheckedModeBanner: false,
    );
  }
}

class DashboardScreen extends StatefulWidget {
  const DashboardScreen({super.key});

  @override
  State<DashboardScreen> createState() => _DashboardScreenState();
}

class _DashboardScreenState extends State<DashboardScreen> {
  @override
  Widget build(BuildContext context) {
    final screenHeight = MediaQuery.of(context).size.height;

    return Scaffold(
      appBar: AppBar(),
      body: CustomScrollView(
        physics: ClampingScrollPhysics(),
        slivers: <Widget>[
          // your build header widget

          SliverToBoxAdapter(
            child: Container(
              width: 100,
              height: 65,
              child: Padding(
                padding: const EdgeInsets.only(top: 20),
                child: ElevatedButton(
                  onPressed: () {},
                  child: Text(
                    'Add',
                    style: TextStyle(fontSize: 18),
                  ),
                  style: ElevatedButton.styleFrom(
                    shape: StadiumBorder(),
                    backgroundColor: Colors.red,
                  ),
                ),
              ),
            ),
          ),
          SliverToBoxAdapter(
            child: SizedBox(height: 10),
          ),
          SliverList(
            delegate: SliverChildBuilderDelegate((context, index) {
              return Container(
                margin: const EdgeInsets.symmetric(
                  vertical: 10.0,
                  horizontal: 20.0,
                ),
                padding: const EdgeInsets.all(10.0),
                height: screenHeight * 0.15,
                decoration: BoxDecoration(
                  gradient: LinearGradient(
                    colors: [Color(0xFFAD9FE4), Colors.red],
                  ),
                  borderRadius: BorderRadius.circular(20.0),
                ),
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceAround,
                  children: <Widget>[
                    // Image.asset(
                    //   "assets/worker.png",
                    //   height: 80,
                    //   width: 80,
                    // ),
                    // 
                    Container(
                    height: 80,
                    width: 80,
                    child: Text("A"),
                    ),
                    
                    Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: <Widget>[
                        Text(
                          'Somme: 50 €',
                          style: const TextStyle(
                            color: Colors.white,
                            fontSize: 18.0,
                            fontWeight: FontWeight.bold,
                          ),
                        ),
                        SizedBox(height: screenHeight * 0.01),
                        Text(
                          'Date: 19 novembre 2022',
                          style: TextStyle(fontSize: 10, color: Colors.white),
                        ),
                        SizedBox(height: screenHeight * 0.01),
                        Text(
                          'Follow the instructionsnto do your own test.',
                          style: const TextStyle(
                            color: Colors.white,
                            fontSize: 16.0,
                          ),
                          maxLines: 2,
                        ),
                      ],
                    )
                  ],
                ),
              );
            }),
          )
        ],
      ),
    );
  }
}