Module not found

Download example with Vaadin 14.0.0RC3
https://vaadin.com/start/latest

What does this error mean?

ERROR in ../target/frontend/generated-flow-imports.js?babel-target=es5
Module not found: Error: Can't resolve '@vaadin/flow-frontend/vaadin-grid-flow-selection-column.js?babel-target=es5' in '/Users/lesharb/workspace/vaadin/simple-app-html/target/frontend'
 @ ../target/frontend/generated-flow-imports.js?babel-target=es5 27:0-68

ERROR in ../target/frontend/generated-flow-imports.js?babel-target=es6
Module not found: Error: Can't resolve '@vaadin/flow-frontend/vaadin-grid-flow-selection-column.js?babel-target=es6' in '/Users/lesharb/workspace/vaadin/simple-app-html/target/frontend'
 @ ../target/frontend/generated-flow-imports.js?babel-target=es6 27:0-68

mvn clean install

[INFO]
 package.json updated and npm dependencies installed. 
[WARNING]
 Do not use the 'frontend://' protocol in '@JsModule', changing 'frontend://styles/shared-styles.js' to './styles/shared-styles.js', please update your component.
[WARNING]
 Use the './' prefix for files in JAR files: 'flow-component-renderer.js', please update your component.
[INFO]
 

  Failed to find the following imports in the `node_modules` tree:
      ➜ @vaadin/flow-frontend/datepickerConnector.js
       ➜ @vaadin/flow-frontend/contextMenuConnector-es6.js
       ➜ @vaadin/flow-frontend/comboBoxConnector.js
       ➜ @vaadin/flow-frontend/gridConnector.js
       ➜ @vaadin/flow-frontend/contextMenuConnector.js
       ➜ @vaadin/flow-frontend/gridConnector-es6.js
       ➜ @vaadin/flow-frontend/flow-component-renderer.js
       ➜ @vaadin/flow-frontend/comboBoxConnector-es6.js
       ➜ @vaadin/flow-frontend/vaadin-grid-flow-selection-column.js
  If the build fails, check that npm packages are installed.

Sounds like a bug. Which example did you choose?

simple-app-html.zip

simple-app-plain-java.zip

I just did not understand what the difference = (

17762320.zip (181 KB)
17762323.zip (181 KB)

I’d try mvn clean package. You can also try to backup and then delete your node_modules folder. mvn package should re-download them again.