babel JS file can't resolve "@babel/runtime/helpers/builtin/classCallCheck"

Since Babel 7.x is still a beta version, there was a breaking change in beta.56, which was released yesterday.

"@babel/runtime": "^7.0.0-beta.56",

If you're using a beta version of something, it is dangerous to use ^ in your version number, because that means it will accept any recent version, whether or not it is actually compatible with previous beta versions.

Since react-scripts uses https://github.com/facebook/create-react-app/blob/1407287839f94151cec729bd89441d4eee7d9dd3/packages/babel-preset-react-app/package.json#L28

"@babel/plugin-transform-runtime": "7.0.0-beta.46",

Your should likely have

"@babel/runtime": "7.0.0-beta.46",

in your own package.json to match.

In my case the problem was in relative paths and complex project structure, so that I had to specify exact location of my node_modules directory:

module.exports = {  
    resolve: {
      modules: [
        path.resolve(__dirname, "node_modules")
      ],
  ...

In case you are running into this because of your dependency on material-ui:

Looks like material-ui updated its package.json to reference '7.0.0-beta.42' instead of '^7.0.0-beta.42'

See Issue: 12409