Can't watch the result of sample code

The error which displayed in the sandpack panel is
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Unable to establish connection with the sandpack bundler. Make sure you are online or try again later. If the problem persists, please report it via [email](mailto:hello@codesandbox.io?subject=Sandpack%20Timeout%20Error) or submit an issue on [GitHub.](https://github.com/codesandbox/sandpack/issues)
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