I am trying to format the tooltip in a highcharts bubble chart

There is a lot of information I'd like to display with custom formats etc so I'm using the formatter function. It is all working fine except for the last line which is a html link (href tag). I want to be able to click on this link in the tooltip and be redirected to the new page however, currently, even though I can see the row highlighted with a link, I'm not being able to click on the link when it renders in the tooltip

Here's the code

const chartOptions  = {
        chart: {
            type: 'bubble',
            plotBorderWidth: 1,
            zoomType: 'xy',
            height: 600,
        },
        title: {text: null},
        legend: {
            enabled: true
        },
        
        tooltip: { 
                useHTML: true,
                formatter: function () {
                    return '<b>' + Highcharts.dateFormat('%e-%b', new Date(this.x)) + ' ' + this.y + '</b><br/>' +
                        '<b>' + 'ACV: ' + '</b>'+ '$' + Math.round(this.point.ACV / 1000).toFixed(1) + 'K' + '<br/>' +
                        'Type: ' + this.point.OPP_COB +  '<br/>' + 'Name: ' + this.point.REP_NAME + '<br/>' + 
                        'Link: ' + '<a href="http://www.mywebsite.com/"' + this.point.customID + ' target="_blank"> Click here </a>'
                        
                }
        },
}

I've tried lots of options for a while but haven't had any luck. Any help would be much appreciated. Thanks