HighCharts：基本折线图不会在X轴上显示第一个标签

下面是我的图形代码，问题是它不会在x轴上显示第一个标签。我尝试了所有选项，如showFirstLabel和startOnTick设置为true。仍然没有显示。HighCharts：基本折线图不会在X轴上显示第一个标签

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);

enter image description here