Why is the webpack config not loading when using Next.js?

Question

React

Hi everyone, I'm working with React/Redux/Next.js. First I created a React / Redux base, now I started integrating Next. Changed package.json :

"start": "webpack-dashboard -- webpack-dev-server --mode development --open --hot",

I imported the
"start": "next",
App.js component into pages/index.js :

import React from "react";
import App from "../src/containers/App";

const Index = ({}) => (
  <div>
    <App />
  </div>
);

export default Index;

and returned:
Error in ./index.scss
Module parse failed: Unexpected token (1:0) You may need an appropriate loader to handle this file type. | .preview { | min-width: 100vw; | min-height: 100vh;
app.js :

import React, { Component } from "react";
import { connect } from "react-redux";
import { initAction } from "../../actions/index";
import "./index.scss";

class App extends Component {
  componentWillMount() {
    const initActionData = {
      hello: "world"
    };
    this.props.initAction(initActionData);
  }

  state = {
    preview: "img/index.jpg"
  };

  render() {
    const { preview } = this.state;
    return (
      <div className="preview" style={{backgroundImage: `url(${preview})`}} />
    );
  }
}
const mapDispatchToProps = {
  initAction
};
const mapStateToProps = state => {
  return {
    init: state.init
  };
};
export default connect(mapStateToProps, mapDispatchToProps)(App);

Didn't work with Next.js before. How to treat this? And how much more will come up during integration?