"props should be defined" but how? - reactjs

Question

I am new to react and react native.
I am trying to set up a simple app, using this tutorial
https://github.com/aksonov/react-native-router-flux/blob/master/docs/MINI_TUTORIAL.md
I have set up my app with this command
create-react-native-app my-project
I start the app and see it in expo on my phone.
Then
npm i react-native-router-flux --save
I replace the contents of App.js with all the code from that tutorial. I also create the required PageOne.js and PageTwo.js.
I then get an immediate error on my phone.
[react-native-router-flux] props should be defined
assert
c:\my path...\react-native-router-flux\src\Util.js#34:10
How do I define these props? What do I need to do to get this working?
Extras!
The code is exactly as in that tutorial,
App.js
import React, { Component } from 'react';
import { Router, Scene } from 'react-native-router-flux';
import PageOne from './PageOne';
import PageTwo from './PageTwo';
export default class App extends Component {
render() {
return (
<Router>
<Scene key="root">
<Scene key="pageOne" component={PageOne} title="PageOne" initial={true} />
<Scene key="pageTwo" component={PageTwo} title="PageTwo" />
</Scene>
</Router>
)
}
}
PageOne.js
import React, { Component } from 'react';
import { View, Text } from 'react-native';
import { Actions } from 'react-native-router-flux';
export default class PageOne extends Component {
render() {
return (
<View style={{margin: 128}}>
<Text onPress={Actions.pageTwo}>This is PageOne! </Text>
</View>
)
}
}
PageTwo.js
import React, { Component } from 'react';
import { View, Text } from 'react-native';
import { Actions } from 'react-native-router-flux';
export default class PageTwo extends Component {
render() {
return (
<View style={{margin: 128}}>
<Text onPress={Actions.pageOne}>This is PageTwo!</Text>
</View>
)
}
}

Answer 1

I don't really have a conclusive answer. Perhaps just being new to a lot of different moving parts had caused something to get out of line.
I updated some magic numbers in package.json and app.json according to the upgrade table on this page
https://github.com/react-community/create-react-native-app/blob/master/VERSIONS.md
and things started to work again.
I suppose that some of my thrashing around installing various react things had gotten the installed versions out of step. Perhaps if I really understood the ecosystem it would seem clear to me but it feels like a bunch of string and bailing wire at the moment!