Mix not processing scss files

I have freshly installed node, and laravel 5.4.5. Then i ran npm install. After that i'm trying to run npm run dev, and I have next error:

ERROR  Failed to compile with 1 errors

 error  in ./resources/assets/sass/app.scss

Module parse failed: C:\OpenServer\domains\triton-barns\resources\assets\sass\app.scss Unexpected token (1:0)
You may need an appropriate loader to handle this file type.
| .app-ticket{
|   overflow:hidden;
|

 @ multi ./mix-entry.js ./resources/assets/sass/app.scss
                                                                                                                                                                                                                                            Asset      Size  Chunks             Chunk Names
           mix.js   2.95 kB       0  [emitted]  mix
mix-manifest.json  24 bytes          [emitted]

npm ERR! Windows_NT 10.0.10586
npm ERR! argv "C:\\Program Files\\nodejs\\node.exe" "C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npm-cli.js" "run" "dev"
npm ERR! node v6.9.4
npm ERR! npm  v3.10.10
npm ERR! code ELIFECYCLE
npm ERR! @ dev: `node node_modules/cross-env/bin/cross-env.js NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js`
npm ERR! Exit status 2

But, If i run : node node_modules/cross-env/bin/cross-env.js NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js

I get next error

ERROR  Failed to compile with 1 errors

 error  in ./resources/assets/sass/app.scss

Module parse failed: \resources\assets\sass\app.scss Unexpected token (1:0)
You may need an appropriate loader to handle this file type.
| .app-ticket{
|   overflow:hidden;
|

 @ multi ./mix-entry.js ./resources/assets/sass/app.scss

            Asset      Size  Chunks             Chunk Names
           mix.js   2.95 kB       0  [emitted]  mix
mix-manifest.json  24 bytes          [emitted]

Here is my webpack.mix.js

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

/*
 |--------------------------------------------------------------------------
 | Mix Asset Management
 |--------------------------------------------------------------------------
 |
 | Mix provides a clean, fluent API for defining some Webpack build steps
 | for your Laravel application. By default, we are compiling the Sass
 | file for the application as well as bundling up all the JS files.
 |
 */

mix.sass('resources/assets/sass/app.scss', 'public/css');

I've googled for 3 hours already, but there is no clear answer jor the problem.

My package.json

{
  "private": true,
  "scripts": {
    "dev": "node node_modules/cross-env/bin/cross-env.js NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
    "watch": "node node_modules/cross-env/bin/cross-env.js NODE_ENV=development node_modules/webpack/bin/webpack.js --watch --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
    "hot": "node node_modules/cross-env/bin/cross-env.js NODE_ENV=development node_modules/webpack-dev-server/bin/webpack-dev-server.js --inline --hot --config=node_modules/laravel-mix/setup/webpack.config.js",
    "production": "node node_modules/cross-env/bin/cross-env.js NODE_ENV=production node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js"
  },
  "devDependencies": {
    "axios": "^0.15.2",
    "bootstrap-sass": "^3.3.7",
    "jquery": "^3.1.0",
    "laravel-mix": "^0.5.0",
    "lodash": "^4.16.2",
    "vue": "^2.0.1"
  }
}