npm start or npm run webapp:build.npm install. If you are behind a corporate proxy, it is likely that this
error was caused by your proxy. Have a look at the error logs, you will probably have the cause of the error.
If you want to go fast, run maven to build and run everything.
If you want to have more control, so you can debug your issue more easily, you should follow the following steps:
npm installnpm run webapp:build or
npm start
mvn or using your IDE