Hey @Chong_Toby, welcome to Streamlit!
This sounds like a frontend error - that is, something in your component’s frontend is triggering an exception, and then React is catching that exception, but it’s not able to show you the exception for some browser security reason.
You say you’re using the template - have you made any modifications to the code itself, or was this triggered just by installing the
react-compound-slider npm package?
Also: if you open your browser’s developer console view, do you see any errors being reported in there?
(Edit: for more context on “cross-origin errors” within React - which I was also unfamiliar with - see https://reactjs.org/docs/cross-origin-errors.html)