highchart print chart/chart context menu un-clickable

Question

I use highchart everything works good except for the chart print button is not click-able, below are my highchart implementation and reference image. Any ideas, clues, suggestions, recommendations, help?

$('#chart_portfolio').highcharts({
                        chart: {
                        borderColor: '#ff0000',
                        width: null,
                        height: null
                        },
                        title: {
                            text: false,
                            x: -20 //center
                        },
                        xAxis: {
                            categories: portfolio_creation_date
                        },
                        yAxis: {
                            title: {
                                text: false
                            },
                            plotLines: [{
                                value: 0,
                                width: 1,
                                color: '#ff0000'
                            }]
                        },
                        tooltip: {
                                shared: true,
                                crosshairs: true
                            },  
                        series: [{
                            name: 'Future',
                            data: portfolio_future,
                            color: '#0f00ff'
                        }, {
                            name: 'In Grace Period',
                            data: portfolio_ingrace_period,
                            color: '#fda800'
                        }, {
                            name: 'Arrears',
                            data: portfolio_in_arrears,
                            color: '#f40404'
                        }, {
                            name: 'Good standing',
                            data: portfolio_good_standing,
                            color: '#4da74d'
                        }]
                    }); //end of highcharts 

Issue reference image

Answer 1

Simply set higher zIndex for that button: http://jsfiddle.net/9P5fC/488/

exporting: {
    buttons: {
        contextButton: {
            theme: {
                zIndex: 100   
            }
        }
    }
}