Why React-Native Couldn't start project on Android connection with Expo?

Couldn't start project on Android.

Error : No Android connected device found, and no emulators could be started automatically.

Please connect a device or create an emulator (https://docs.expo.io/workflow/android-studio-emulator).

Then follow the instructions here to enable USB debugging:

https://developer.android.com/studio/run/device.html#developer-device-options. If you are using Genymotion go to Settings -> ADB, select "Use custom Android SDK tools", and point it at your Android SDK directory.

In order to run your React Native application, you first need to run an emulator seperately. It won't start an emulator automatically like a native Android Studio build.

• Create an AVD using this tutorial.

• Note down your AVD name, if you are gonna run it without Android Studio.

• Run below code in a Command Prompt window to start emulator without Android Studio. Assuming that you have installed your SDK in default location, otherwise change it to your location.

  cd C:\Users\%USERNAME%\AppData\Local\Android\Sdk\emulator
  emulator -avd Pixel_2_API_30
  

• Pixel_2_API_30 is the name of AVD so change it to yours.

• Once your emulator is running then you can run your React Native build as stated in this setup guide.