Dialog (app.execDialog()) doesn't open second time i run the script

I'm using Acrobat DC and Windows 10.

Here's the script:

/* Put script title here */
var dialogExh =
{
   initialize: function(dialog)
   {
      // Set default values
      dialog.load(
      {
         "sNum": global.startNum,
         "fSze": global.FontSize,
         "oTxt": global.Label,
         "eNum": global.endNum
      });
   },
   // called when OK pressed
   commit:function (dialog)
   {
      var selections = dialog.store();
      global.startNum = selections["sNum"];
      global.counter = selections["sNum"]-1;
      global.endNum = selections["eNum"];
      global.FontSize = selections["fSze"];
      global.Label = selections["oTxt"].trim();

   },
   destroy:function(dialog)
   {
      console.println("Destroy.");
   },
   description:
   {
      // Dialog box title
      name: "Sequential Slip Sheets - [ALL FOUR BOXES MUST BE FILLED IN]",
      first_tab: "eNum",
      align_children: "align_top",
      bold: true,
      width: 250,
      height: 200,
      elements:
      [
         {
            alignment: "align_left",
            type: "ok_cancel",
            ok_name: "OK",
            cancel_name: "Cancel"
         },
         {
            type: "cluster",
            name: "Label - [ALL BOXES MUST BE FILLED IN]",
            align_children: "align_left",
            elements:
            [
               {
                  item_id: "oTxt",
                  type: "edit_text",
                  alignment: "align_fill",
                  width: 100,
                  height: 20,
               },
               {
                  type: "view",
                  align_children: "align_row",
                  elements:
                  [
                     {
                        type: "static_text",
                        name: "Font Size: ",
                        alignment: "align_left",
                     },
                     {
                        item_id: "fSze",
                        type: "edit_text",
                        alignment: "align_left",
                        width: 50,
                        height: 20,
                     },
                  ]
               },
            ]
         },
         {
            type: "cluster",
            name: "Exhibit Numbers",
            align_children: "align_left",
            elements:
            [
               {
                  type: "view",
                  align_children: "align_row",
                  width: 138,
                  elements:
                  [
                     {
                        type: "static_text",
                        name: "Starting Num: ",
                        alignment: "align_left",
                     },
                     {
                        item_id: "sNum",
                        type: "edit_text",
                        alignment: "align_fill",
                        width: 50,
                        height: 20,
                     },
                  ]
               },
               {
                  type: "view",
                  align_children: "align_row",
                  width: 138,
                  elements:
                  [
                     {
                        type: "static_text",
                        name: "Ending Num: ",
                        alignment: "align_left",
                     },
                     {
                        item_id: "eNum",
                        type: "edit_text",
                        alignment: "align_fill",
                        width: 50,
                        height: 20,
                     },
                  ]
               },
            ]
         }
      ]
   }
};

// Begin job
try {
   if ( typeof global.counter == "undefined" )
   {
      console.println("Begin Job Code");
      global.counter = 0;
      global.startNum = "1";
      global.endNum = "";
      global.FontSize = "40";
      global.Label = "Exhibit";
      console.println("Before Do");
      do
      {
         try
         {
           console.println("Display dialog 1.");
           dialogResult = app.execDialog(dialogExh);
           console.println(dialogResult);
         }
         catch (err)
         {
             console.println("Error Message:  " + err);
         };
         if (dialogResult != "ok")
         {
            throw "Script cancelled.";
         };
         console.println("Display dialog 2.");
      }
      while ( global.Label == "" || global.startNum == "" || global.endNum == "" || global.FontSize == "" );
      global.FileCount = Number(global.endNum) - Number(global.startNum) + 1;
      confirmNum = app.alert(
      {
         cTitle:  "PLEASE CONFIRM",
         nIcon:  3,
         nType: 1,
         cMsg:  "Number of PDFs to process:  " + global.FileCount
      });
      if ( confirmNum == "2" )
      {
          throw "Script cancelled.";
      }; 
   // insert beginJob code here
   };
   global.counter++;
   console.println("Processing File #" + global.counter);
      //insert blank page as new page 1 of the PDF
   this.newPage(0);
   var annot = this.addAnnot
      ({
  page: 0,
  type: "FreeText",
         rect: [72,360,540,576],
         width: 0,
      });
   annot.textFont = "TimesNewRoman";
   var spans = new Array();
   spans[0] = new Object();
   spans[0].text = global.Label + " " + global.counter;
   spans[0].textColor = color.black;
   spans[0].textSize = Number(global.FontSize);
   spans[0].fontWeight = 700;
   spans[0].alignment = "center";

   // Now give the rich field a rich value
   annot.richContents = spans;

   this.flattenPages({
        nStart: 0,
      });
   } catch(e) {
         console.println("Batch aborted on run #" + global.counter);
         delete global.counter; // Try again, and avoid End Job code
         if ( typeof global.FileCount != "undefined" )
         {
            delete global.FileCount;
         }
         event.rc = false; // Abort batch
};
if ( global.counter == global.FileCount )
{
   if ( typeof global.counter != "undefined" )
   {
      console.println("End Job Code");
      // Remove any global variables used in case user wants to run
      // another batch sequence using the same variables
      console.println(global.counter);
      delete global.counter;
   };
   if ( typeof global.FileCount != "undefined" )
   {
      // Remove any global variables used in case user wants to run
      // another batch sequence using the same variables
      console.println(global.FileCount);
      delete global.FileCount;
   };
};
// End job