How to Prevent Duplicate Entries in Google Forms and Notify Users Using Google Apps Script

I'm working on a project where I need to prevent duplicate entries in a Google Form based on a barcode number field. When a duplicate barcode number is detected upon form submission, the submission should be rejected, and both the submitter and a designated recipient should be notified via email.

Requirements:

Prevent duplicate entries based on the barcode number.Notify both the submitter and a designated recipient if a duplicate is detected.Automate the process without manual intervention.What I’ve Done:

Created a Google Form with fields for Barcode Number and Submitter's Email.Linked the form to a Google Sheets document.Wrote the following Google Apps Script to check for duplicates and send emails:

function onFormSubmit(e) {  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();  var lastRow = sheet.getLastRow();  var barcodeIndex = 1; // Adjust this index based on the position of the Barcode Number column in your form responses  var emailIndex = 2; // Adjust this index based on the position of the Submitter's Email column in your form responses  if (lastRow > 1) {    var newBarcode = e.values[barcodeIndex];    var submitterEmail = e.values[emailIndex];    var existingBarcodes = sheet.getRange(2, barcodeIndex + 1, lastRow - 1, 1).getValues().flat();    if (existingBarcodes.includes(newBarcode)) {      // If a duplicate is found, delete the latest row (the current submission)      sheet.deleteRow(lastRow);      // Send email notification about the duplicate      var recipientEmail = "my-email@example.com"; // Replace with your email      var subject = "Duplicate Entry Detected";      var message = "A duplicate entry for Barcode Number " + newBarcode +" was detected and not accepted.";      // Send email to the designated recipient      MailApp.sendEmail({        to: recipientEmail,        subject: subject,        body: message      });      // Send email to the submitter      MailApp.sendEmail({        to: submitterEmail,        subject: subject,        body: message      });      return;    }  }}function createTrigger() {  var ss = SpreadsheetApp.getActiveSpreadsheet();  ScriptApp.newTrigger('onFormSubmit')           .forSpreadsheet(ss)           .onFormSubmit()           .create();}

Issues:

The script doesn't seem to detect duplicates properly.Fails to delete the row and send the emails when a duplicate is found.Could anyone provide guidance on how to properly set this up? Any help would be greatly appreciated!

Thanks in advance!