I want to modify component css, the use it in app, but it wrong. how to do?

I download hydralit_components code source, i want to change the css, but after run ,it display error, what is happened?

Your app is having trouble loading the **Navbar.nav_bar** component.

(The app is attempting to load the component from **[http://localhost:3000](http://localhost:3000/)**, and hasn't received its **"streamlit**

**"** message.)

* If this is a development build, have you started the dev server?
* If this is a release build, have you compiled the frontend?

For more troubleshooting help, please see the [Streamlit Component docs](https://docs.streamlit.io/library/components) or visit our [forums](https://discuss.streamlit.io/).