If you've worked with React Native for a while, you've probably run into a problem where Metro refuses to start, gets stuck while bundling, or leaves your app waiting for JavaScript that never arrives.

Sometimes the terminal shows an error immediately. Other times, Metro appears to start normally, but the app stays on a loading screen or fails to connect to the development server.

The frustrating part is that these symptoms can have completely different causes. A port conflict, stale cache, broken dependency installation, invalid configuration, or network issue can all look like a Metro problem.

Here's how to narrow it down and fix the actual cause instead of repeatedly restarting your project and hoping something changes.

1.…