The server for which the cat images were being source is down (https://placekitten.com/)

[onlinemax]

Summary

The images are simply not loading because the server that hosted them is down.

Page

https://react.dev/learn/manipulating-the-dom-with-refs

Details

You can find the specified images in the sandbox below the subheading: Example: Scrolling to an element.

[rammba]

This is fixed in #7189, so it can be closed.

[rickhanlonii]

Yup, fixed in https://github.com/reactjs/react.dev/pull/7189