if reopened is what needs to be kept track of, i would
    read the reopened attribute value and
    on finding that it is already true,
    just return back the value with no further processing..

in your case, i see a similar approach using
   var reopen = workItem.getValue(WorkItemAttributes.REOPENED);

however, I believe you are working with a custom attribute of type boolean and not a built in attribute.  Only some of the built-in attributes can be read using the
    var WorkItemAttributes= com.ibm.team.workitem.api.common.WorkItemAttributes;
followed by
    workItem.getValue(WorkItemAttributes.REOPENED);

what you would require is to use the ID of the custom attribute provided to the workItem.getValue API in double quotes, as in
    workItem.getValue("customAttributeID");


here is a sample script that works for me:

dojo.provide("com.example.ValueProvider.setCheckBool");
dojo.require("com.ibm.team.workitem.api.common.WorkItemAttributes");
(function() {
var WorkItemAttributes= com.ibm.team.workitem.api.common.WorkItemAttributes;
    dojo.declare("com.example.ValueProvider.setCheckBool", null, {
    getValue: function(attribute, workItem, configuration) {

  var ret = "False";
    var reopen = workItem.getValue("checkbool");
   var state = workItem.getValue(WorkItemAttributes.STATE); 
  
   console.log("State is : " + state + " and Reopened : " + reopen);
  
   if( reopen == true){
      ret="true";
   }
  
   if (state == "3"){
   ret="true";
   }
           
   return ret;}

    });
})();

this might as well be the reason for the Problems in loading the script.