Error the mix manifest does not exitst

[shlyap1k]

After deploy on heroku, I see an error The Mix manifest does not exist. (View: /app/resources/views/landing.blade.php) when open it in browser, but it works when in package.json in scripts I write npm run dev instead of production. Is there some problems with dev or it may be worked as is?

You can check it here: https://shlyapik.herokuapp.com/