Not working in IOS, getting "Null is not an object in Beacons.requestWhenInUseAuthorization();"

import React from 'react';
import {
Dimensions,
ImageBackground,
TouchableOpacity,
View,
StatusBar,
Platform,
Alert,
DeviceEventEmitter
} from 'react-native';
import Pulse from 'react-native-pulse';
import _map from 'lodash/map';
import Reactotron from 'reactotron-react-native';
import ScalableText from 'react-native-text';
import { connect } from 'react-redux';
import RNModal from 'react-native-modal';
import { NavigationEvents } from 'react-navigation';
import Icon from 'react-native-vector-icons/Ionicons';
import _filter from 'lodash/filter';
import _intersectionBy from 'lodash/intersectionBy';
import _forEach from 'lodash/forEach';
import Beacons from 'react-native-beacons-manager';

class PulseScreen extends React.Component {

startBeacon = () => {
	if (Platform.OS === 'ios') {
		Reactotron.log('iosPLatform');
		const region = {
			identifier: 'estimote',
			uuid: '1a9f0cfb7d4bfc0e3071bffe2455261e'
		};
		Beacons.requestAlwaysAuthorization();
		Beacons.startRangingBeaconsInRegion(region)
			.then((data) => {
				Alert.alert('', `Beacons monitoring started!`);
			})
			.catch((error) => {
				Alert.alert('', `Beacons start error! IOS`);
			});
		DeviceEventEmitter.addListener('beaconsDidRange', (data) => {
			Alert.alert('', 'beacons monitering started')
			if (data.beacons.length) {
				this.setState({ detectedBeacons: data.beacons });
				Alert.alert(`Found beacons!`, JSON.stringify(data.beacons));
			}
		});

		Beacons.startUpdatingLocation();
	}
	else {
		Reactotron.log('else');
		Beacons.detectIBeacons();
		Beacons.detectAltBeacons();
		Beacons.detectEstimotes();
		Beacons.detectEddystoneUID();
		Beacons.detectEddystoneTLM();
		Beacons.detectEddystoneURL();
		Beacons.startRangingBeaconsInRegion('REGION1')
			.then((data) => {
				Alert.alert('', `Beacons monitoring started!`);
			})
			.catch((error) => {
				Alert.alert('', `Beacons start error!`);
			});
		DeviceEventEmitter.addListener('beaconsDidRange', (data) => {
			if (data.beacons.length) {
				this.setState({ detectedBeacons: data.beacons });
				Alert.alert(`Found beacons!`, JSON.stringify(data.beacons));
			}
		});
	}
};

render() {
	const { nearbyStores } = this.state;
	const { beaconList } = this.props;

	return (
		<View><NavigationEvents
				onWillFocus={() => {
					StatusBar.setBarStyle('light-content', true);
					if (beaconList.length) {
						this.startBeacon();
					}
				}}
				onWillBlur={() => {
					if (beaconList.length) {
						Beacons.stopRangingBeaconsInRegion('REGION1')
							.then(() => {
								Alert.alert('', `Beacons monitoring stopped succesfully!`);
							})
							.catch((error) => {
								Alert.alert(`Beacons stop error!`);
							});
					}
					StatusBar.setBarStyle('dark-content', true);
				}}
			/>