Browsersync not responding


I’m trying to develop a Wordpress Theme with Roots Sage. I’ve got a fresh install of Wordpress and Sage.
When i do yarn start Browsersync gives me:

[BS] [HTML Injector] Running...
[Browsersync] Proxying: http://test.local
[Browsersync] Access URLs:
       Local: http://localhost:3000
    External: http://xxx:3000
          UI: http://localhost:3001
 UI External: http://xxx:3001
[Browsersync] Watching files...

and a Browsertab opens. Unfortunately the page just keeps loading but without any response.

Webpack config ( resources/assets/build/webpack.config.js ) is

  "entry": {
    "main": [
    "customizer": [
  "publicPath": "/wp-content/themes/my-theme",
  "devUrl": "http://test.local",
  "proxyUrl": "http://localhost:3000",
  "cacheBusting": "[name]_[hash:8]",
  "watch": [

Any ideas?