If you used npm, install yarn (http://yarnpkg.com/) and repeat the above steps with it instead. This may help because npm has known issues with package hoisting which may get resolved in future versions. code example
Example 1: There might be a problem with the project dependency tree. It is likely not a bug in Create React App, but something you need to fix locally.
"react-scripts": "<whatever-is-currently-here>",
"react-scripts": "1.1.4",
Example 2: If you would prefer to ignore this check, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project. That will permanently disable this message but you might encounter other issues.
yarn add --dev dotenv
SKIP_PREFLIGHT_CHECK=true