npm run prod not generating css

[urfusion]

• Laravel Mix Version: #.#.# (npm list --depth=0)
  ├── accounting@0.4.1
  ├── axios@0.21.4
  ├── bootstrap-sass@3.4.3
  ├── cross-env@5.2.1
  ├── eslint@8.45.0
  ├── font-awesome@4.7.0
  ├── jquery@3.7.0
  ├── laravel-mix@2.1.14
  ├── laravel-mix-merge-manifest@0.1.2
  ├── laravel-mix-prerender@0.1.0-rc.5 extraneous
  ├── lazysizes@5.3.2
  ├── material-icons@0.7.7
  ├── vee-validate@2.2.15
  ├── vue@2.7.14
  ├── vue-carousel@0.18.0
  ├── vue-single-select@1.1.0
  └── vue-slider-component@3.2.24

npm ERR! extraneous: laravel-mix-prerender@0.1.0-rc.5 /var/www/html/packages/My/Luso/node_modules/laravel-mix-prerender
npm ERR! peer dep missing: imagemin@^5.0.0 || ^6.0.0 || ^7.0.0, required by img-loader@3.0.2
npm ERR! peer dep missing: @types/webpack@>4.41.31, required by webpack-notifier@1.15.0

• Node Version (node -v):
  v12.0.0

• NPM Version (npm -v):
  6.9.0

• OS:
  Ubuntu

I am using Laravel with VueJS and, for generating optimized CSS and JS, I am using webpack.mix.js.

When I run npm run dev, CSS files are generated quite fine while if I run npm run prod, it generates CSS of 1 byte.

Here is my webpack.mix.js

const {mix} = require('laravel-mix');

require('laravel-mix-merge-manifest');

let publicPath = '../../../public/themes/mytheme/assets';

if (mix.inProduction()) {
    publicPath = 'publishable/assets';
}

mix.setPublicPath(publicPath).mergeManifest();
mix.disableNotifications();

try {
    mix
        .js(__dirname + '/src/Resources/assets/js/app-core.js', 'js/velocity-custom-core.js')
        .js(
            __dirname + '/src/Resources/assets/js/app.js',
            'js/velocity-custom.js'
        )

        .copy(__dirname + '/src/Resources/assets/images', publicPath + '/images')

        .sass(
            __dirname + '/src/Resources/assets/sass/admin.scss',
            __dirname + '/' + publicPath + '/css/velocity-admin.css'
        )
        .sass(
            __dirname + '/src/Resources/assets/sass/app.scss',
            __dirname + '/' + publicPath + '/css/velocity.css',
            {includePaths: ['node_modules/bootstrap-sass/assets/stylesheets/']}
        )

        .options({
            processCssUrls: false
        })
        .styles(
            [
                publicPath + '/css/header.css',
                publicPath + '/css/listing-style.css',
                publicPath + '/css/custom-listing-desktop-combined.css'
            ],
            __dirname + '/' + publicPath + '/css/custom-listing-desktop-combined.css'
        )
        .scripts(
            [
                publicPath + '/js/jquery-3.6.0.min.js',
                publicPath + '/js/intlTelInput.min.js',
                publicPath + '/plugins/bootstrap_v5.1/js/bootstrap.bundle.js',
                publicPath + '/js/modernizr-3.11.2.min.js',
                publicPath + '/plugins/Swiper/swiper-bundle.min.js',
                publicPath + '/plugins/sweetalert2/sweetalert2.min.js',
                publicPath + '/plugins/toastr/toastr.min.js',
                publicPath + '/js/jwt-decode.js',
            ],
            __dirname + '/' + publicPath + '/css/custom-combined.js'
        );

    if (mix.inProduction()) {
        mix.minify([__dirname + '/' + publicPath + '/css/custom-combined.css']); // Minify the combined CSS file
        mix.version();
    }
} catch (error) {
    console.error('Error during asset compilation: ' + error.message);
}