Following code doesn't update the custom object on contact anybody can me help to find error

global class calculateBooking implements Database.Batchable<sObject>{
  //global  Integer intNumberOfBooking ;
  
    global Database.QueryLocator start(Database.BatchableContext BC){
        //String gstrQuery = 'SELECT Contact_ID__c, Most_Recent_Booking__c, Name,Last_6_Months__c from Booking_Details__c';
        String gstrQuery = 'SELECT ID,Name,Salesforce_Contact_ID__c from Contact';
        return Database.getQueryLocator(gstrQuery);
    } 


global void execute(Database.BatchableContext BC, List<sObject> scope){
    
    
     List<Booking_Details__c> listBookingInsert = new List<Booking_Details__c>();
      List<Booking_Details__c> listBookingUpdate = new List<Booking_Details__c>();
      List<Booking_Details__c> listBooking= [SELECT Booking_Salesforce_Contact_ID__c, Most_Recent_Booking__c, Name,Last_6_Months__c from Booking_Details__c];
     //List<Contact> listContact = new List<Contact>();
      for(SObject objSObject : scope)
      {
          //Booking_Details__c objBooking = (Booking_Details__c)objSObject;
          Contact objContact = (Contact) objSObject;
          Integer intNumberOfBooking = [SELECT count()FROM Booking__c WHERE Contact__C = :objContact.ID AND Date_Time__c = LAST_N_DAYS:365];
          for(Booking_Details__c bd: listBooking)
          {
           if (bd.Contact_ID__c==objContact.ID)
           {
                bd.Last_6_Months__c = intNumberOfBooking+6;
                //bd.Booking_Salesforce_Contact_ID__c= objContact.Salesforce_Contact_ID__c;
                //objBooking.Name =;
                listBookingUpdate.add(bd);         
           }
           
           
          }
      }
      //insert listBookingInsert;
        update listBookingUpdate;
      //System.debug('Update');
      

     
}
  
global void finish(Database.BatchableContext BC){
  //  System.debug(intNumberOfBooking);   
    System.debug('Finish');
    /*//Send an email to the User after your batch completes
            AsyncApexJob a =[SELECT Id, Status, NumberOfErrors, JobItemsProcessed,
        TotalJobItems, CreatedBy.Email
        FROM AsyncApexJob WHERE Id =
        :BC.getJobId()];
        // Send an email to the Apex job's submitter
        // notifying of job completion.
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
        String[] toAddresses = new String[] {a.CreatedBy.Email};
        mail.setToAddresses(toAddresses);
        mail.setSubject('Record Clean Up Status: ' + a.Status);
        mail.setPlainTextBody
        ('The batch Apex job processed ' + a.TotalJobItems +
        ' batches with '+ a.NumberOfErrors + ' failures.');
        Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
        */}
}