- This is either due to a require() error during initialisation or failure to call AppRegistry.registerComponent.

I had been struggling with this for some time and the answer was right there… I had to make sure I called AppRegistry.registerComponent with the right params/appname – I had renamed my app and forgot to update the class name and also the name passed to registerComponent.

And, one way to rename a project is by renaming in package.json and then running react-native upgrade.