HighCharts：基本折線圖不會在X軸上顯示第一個標籤

下面是我的圖形代碼，問題是它不會在x軸上顯示第一個標籤。我嘗試了所有選項，如showFirstLabel和startOnTick設置爲true。仍然沒有顯示。HighCharts：基本折線圖不會在X軸上顯示第一個標籤

var my_chart = { 
     chart: { 
      renderTo: 'divSigninGraph', 
      marginTop: 5, 
      fontFamily: 'Arial,Helvetica,sans-serif', 
      zoomType: 'xy' 
     }, 
     credits: { 
      enabled: false 
     }, 
     title: { 
      style: { 
       display: 'none' 
      } 
     }, 
     legend: { 
     enabled: false 
     }, 
     exporting: { 
      enabled: false 
     }, 
     plotOptions: { 
      series: { 
       animation: { 
        duration: 3000 
       } 
      } 
     }, 
     series: [ 
      { 
       type: 'line', 
       name: 'Your Progress', 
       color: '#27aae2', 
       data: [7, 0, 1, 19, 50, 5, 0, 0, 0, 2, 2, 6, 2, 0, 1, 1, 0, 0, 9, 0, 0, 7, 9, 2, 9, 0, 0, 0, 0, 0, 1] 
      } 
      ], 
     xAxis: { 
     startOnTick:true, 
     showFirstLabel: true, 
     endOnTick : true, 
     showLastLabel:true, 

      categories: ['Jun 24', 'Jun 25', 'Jun 26', 'Jun 27', 'Jun 28', 'Jun 29', 'Jun 30', 'Jul 1', 'Jul 2', 'Jul 3', 'Jul 4', 'Jul 5', 'Jul 6', 'Jul 7', 'Jul 8', 'Jul 9', 'Jul 10', 'Jul 11', 'Jul 12', 'Jul 13', 'Jul 14', 'Jul 15', 'Jul 16', 'Jul 17', 'Jul 18', 'Jul 19', 'Jul 20', 'Jul 21', 'Jul 22', 'Jul 23', 'Jul 24'], 
      labels: { 
       align: 'right', 
       rotation: -90, 
       step: 30,      
       style: { 
        font: 'normal 9px Arial' 
       } 
      } 
     }, 
     yAxis: { 
     title: { 
      text: null 
     }, 
     labels: { 
      enabled: false 
     } 
    } 
    }; 
    new Highcharts.Chart(my_chart);

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