Problem

I was running React Native on iOS and got the error:

error Failed to launch the app on simulator, An error was encountered processing the command (domain=com.apple.CoreSimulator.SimError, code=405):
Unable to lookup in current state: Shutdown

Solution

Delete Xcode cache by selecting  > System Settings… > General > Storage > Developer ⓘ > Xcode Caches and Project Build Data and Indexes > Delete…

Rerun React Native and open the Simulator device:

npx react-native run-ios