warn No apps connected. Sending "reload" to all React Native apps failed. Make sure your app is running in the simulator or on a phone connected via USB. info Reloading app... warn No apps connected. Sending "devMenu" to all React Native apps failed. Make sure your app is running in the simulator or on a phone connected via USB. info Opening developer menu... N
1.我这个问题出现的原因一开始是因为的node安装的是12.19.1版本，然后经过确认需要安装12.9.1版本，所以我node重新安装了.
2.重新安装之后还是这个错误，然后我突然想起来我rn全局那个 React Native CLI是用12.19.1安装的，可能有问题，于是重新卸载和安装
npm uninstall react-native-cli npm install -g react-native-cli //因为我安装教程安装的是全局的，所以要卸载掉重新安装，包括npm包
3.然后就搞定了，进入这个界面
原文：https://www.cnblogs.com/shuen/p/14874206.html