App.js

import React from 'react';
import {Appbar, BottomNavigation, Provider as PaperProvider} from 'react-native-paper';
import {Provider, connect} from 'react-redux';
import {createStore} from 'redux';

import Theme from './styles/theme';
import Screens from './screens';

/*
{ key: 'Settings', title: 'Settings', icon: 'settings', color: Theme.colors.primary }, //, color: '#00796b'
			{ key: 'Editor', title: 'Editor', icon: 'edit', color: Theme.colors.primary }, //, color: '#c51162'
			{ key: 'Calendar', title: 'Calendar', icon: 'perm-contact-calendar', color: Theme.colors.primary }, //, color: '#dca627'
			{ key: 'Reminders', title: 'Reminders', icon: 'notifications', color: Theme.colors.primary } //, color: '#dca627'
 */

const store = createStore(function(state = {token: ""}, action) {
	switch (action.type) {
		default:
			return state;
	}
});

class App extends React.Component {
	state = {
		index: 0,
		routes: [
			{ key: 'Login', title: 'Log In', icon: 'vpn-key', color: Theme.colors.primary }, //, color: '#960fee'
			{ key: 'SignUp', title: 'Sign Up', icon: 'lock-outline', color: Theme.colors.primary }, //, color: '#2962ff'
		],
	};

	_handleIndexChange = index => this.setState({ index });

	_renderScene = BottomNavigation.SceneMap(Screens);

	render() {
		return (
			<Provider store={createStore()}>
				<PaperProvider>
					<Appbar.Header theme={Theme}>
						<Appbar.BackAction/>
						<Appbar.Content title="7Days"/>
					</Appbar.Header>
					<BottomNavigation
						navigationState={this.state}
						onIndexChange={this._handleIndexChange}
					 renderScene={this._renderScene}/>
				</PaperProvider>
			</Provider>
		);
	}
}

function mapStateToProps(state) {
	return {
		token: state.token
	}
}

export default connect(mapStateToProps)(App)
// export default App;

App2.js

import React from 'react';
import {Appbar, BottomNavigation, Provider as PaperProvider} from 'react-native-paper';
import {Provider, connect} from 'react-redux';
import {createStore} from 'redux';

import Theme from './styles/theme';
import Screens from './screens';

/*
{ key: 'Settings', title: 'Settings', icon: 'settings', color: Theme.colors.primary }, //, color: '#00796b'
			{ key: 'Editor', title: 'Editor', icon: 'edit', color: Theme.colors.primary }, //, color: '#c51162'
			{ key: 'Calendar', title: 'Calendar', icon: 'perm-contact-calendar', color: Theme.colors.primary }, //, color: '#dca627'
			{ key: 'Reminders', title: 'Reminders', icon: 'notifications', color: Theme.colors.primary } //, color: '#dca627'
 */

const store = createStore(function(state = {token: ""}, action) {
	switch (action.type) {
		default:
			return state;
	}
});

class Main extends React.Component {
	state = {
		index: 0,
		routes: [
			{ key: 'Login', title: 'Log In', icon: 'vpn-key', color: Theme.colors.primary }, //, color: '#960fee'
			{ key: 'SignUp', title: 'Sign Up', icon: 'lock-outline', color: Theme.colors.primary }, //, color: '#2962ff'
		],
	};

	_handleIndexChange = index => this.setState({ index });

	_renderScene = BottomNavigation.SceneMap(Screens);

	render() {
		return (
			<PaperProvider>
				<Provider store={createStore()}>
					<Appbar.Header theme={Theme}>
						<Appbar.BackAction/>
						<Appbar.Content title="7Days"/>
					</Appbar.Header>
					<BottomNavigation
						navigationState={this.state}
						onIndexChange={this._handleIndexChange}
					 renderScene={this._renderScene}/>
				</Provider>
			</PaperProvider>
		);
	}
}

function mapStateToProps(state) {
	return {
		token: state.token
	}
}

export default connect(mapStateToProps)(class App {
	render() {
		return (
			<Main/>
		)
	}
});
// export default App;

App3.js

import React from 'react';
import {View} from 'react-native';
import {Appbar, BottomNavigation, Provider as PaperProvider} from 'react-native-paper';
import {Provider as ReduxProvider, connect} from 'react-redux';
import {createStore} from 'redux';

import Theme from './styles/theme';
import Screens from './screens';

/*
{ key: 'Settings', title: 'Settings', icon: 'settings', color: Theme.colors.primary }, //, color: '#00796b'
			{ key: 'Editor', title: 'Editor', icon: 'edit', color: Theme.colors.primary }, //, color: '#c51162'
			{ key: 'Calendar', title: 'Calendar', icon: 'perm-contact-calendar', color: Theme.colors.primary }, //, color: '#dca627'
			{ key: 'Reminders', title: 'Reminders', icon: 'notifications', color: Theme.colors.primary } //, color: '#dca627'
 */

const store = createStore(function(state = {token: ""}, action) {
	switch (action.type) {
		default:
			return state;
	}
});

class Main extends React.Component {
	state = {
		index: 0,
		routes: [
			{ key: 'Login', title: 'Log In', icon: 'vpn-key', color: Theme.colors.primary }, //, color: '#960fee'
			{ key: 'SignUp', title: 'Sign Up', icon: 'lock-outline', color: Theme.colors.primary }, //, color: '#2962ff'
		],
	};

	_handleIndexChange = index => this.setState({ index });

	_renderScene = BottomNavigation.SceneMap(Screens);

	render() {
		return (
			<PaperProvider>
				<ReduxProvider store={store}>
					<Appbar.Header theme={Theme}>
						<Appbar.BackAction/>
						<Appbar.Content title="7Days"/>
					</Appbar.Header>
					<BottomNavigation
						navigationState={this.state}
						onIndexChange={this._handleIndexChange}
					 renderScene={this._renderScene}/>
				</ReduxProvider>
			</PaperProvider>
		);
	}
}

function mapStateToProps(state) {
	return {
		token: state.token
	}
}

export default connect(mapStateToProps)(class App {
	render() {
		return (
			<View>
				<Main/>
			</View>
		)
	}
});

As app is the root component of the app, you cannot use connect as there is no store in the context above the root component. Change the app class name to something else and then create a new component "App" which you wrap with the store provider. Then connect(mapStateToProps)(otherComponent);