unable to see modal?

I am trying to get modal on click of map marker. I cant see any modal on click of map marker. I am using es6 syntax
here is the code

import Modal from 'react-native-modalbox'
openModal4 = (id) => {
    this.refs.modal4.open();
  }

renderScene () {
    return (
      <View style={style.mainContainer}>
        <MapView
          ref="map"
          style={styles.map}
          rotateEnabled={false}
          showsCompass={false}
          >
          {this.state.markers.map(function(marker){
            return(
              <MapView.Marker coordinate={marker.latlng} key={marker.id} onPress={this.openModal4} />
            );
          })}
        </MapView>
        <View>
          <Image
            source={require('./assets/map-marker.png')}
          />
        </View>
      <Modal style={[styles.modal, styles.modal4]} position={"bottom"} ref={"modal4"}>
        <Text>you are in modal</Text>
        </TouchableOpacity>
      </Modal>
      </View>

can you help me@maxs15.

Start by reproducing the issue from the shown renderScene code, focusing on MapView.Marker's onPress handler and the Modal ref named modal4. Verify whether tapping a marker reaches openModal4 and whether the modal becomes visible; done means the modal opens on marker click or the project documents a confirmed issue with this usage.