Google form approval workflow | issue in Apps Script: "Authorization is required to perform that action."

I am working on a script for leave application via Google forms. I found this script online and have been trying to get it working. When a form is submitted, the script retrieves and populates the linked spreadsheet with the transaction ID, requester's email and places the request status as 'pending'. It then sends an email to the manager and includes links in the email to approve or deny the request.

I have it working up to here which is the onFormSubmit function. This is all working.

When I come to the doGet(e) function, I run into issues. It is supposed to retrieve the managers response and update the spreadsheet status from pending to either approve or deny. An email is then sent to the requester with the outcome.

When I click in the email to either approve or deny a request, I get a message "Authorization is required to perform that action."

When I try to run the doGet(request) function, I get the error: "TypeError: Cannot read property 'parameters' of undefined (line 42)".

var responseID = request.parameters.id;

Is it possible I need to reauthorize the script due to new services? But, this is difficult when I keep returning this error.

Any help or ideas would be greatly appreciated.

Here is the full script:

function onFormSubmit(e) {

 // Open the sheet which stores the responses
 var ssID = 'My Sheet ID' // Replace with spreadsheet ID
 var ssName = 'Form responses' // Replace with sheet name
 var sheet = SpreadsheetApp.openById(ssID).getSheetByName(ssName);

 // #1 - Identify the requestor's email address and save it to the sheet.
 var email = Session.getEffectiveUser().getEmail();
 sheet.getRange(sheet.getLastRow(), 7).setValue(email);

 // #2 - Get the response ID and save it to the sheet.
 var responseID = e.response.getId();
 sheet.getRange(sheet.getLastRow(), 8).setValue(responseID);

 // #3 - Set the status of the request to 'Pending'.
 sheet.getRange(sheet.getLastRow(), 9).setValue('Pending');

 // Create variables for email
 var items = e.source.getItems();
 var manager_email = e.response.getResponseForItem(items[4]).getResponse();
 var subject = "A leave request has been submitted";

 // Include form data in the body of the email
 var message = "";
 for(var i in items)
 message += "\n\n" + items[i].getTitle() + ": " + 
 e.response.getResponseForItem(items[i]).getResponse();

 // #4 - Insert approve and deny links within the body of the email
 message += "\n\nClick link below to approve: https://script.google.com/macros/s/AKfycbxdS3cUP_oSjfphDaSNkn_5GuxxlPG6czVHH_wGJ2OxImqFASmZ/exec?id=" + responseID + "&status=Approved \n\n" + "Click link below to deny: https://script.google.com/macros/s/AKfycbxdS3cUP_oSjfphDaSNkn_5GuxxlPG6czVHH_wGJ2OxImqFASmZ/exec?id=" + responseID + "&status=Denied";

 // #5 - Email the manager the request information
 MailApp.sendEmail(manager_email, subject, message);

}

function doGet(request) {

  // Retrieve the parameter information for response ID and stutus
  var responseID = request.parameters.id;
  var status = request.parameters.status;

  // Open the sheet which stores the responses
  var ssID = 'My Sheet ID' // Replace with spreadsheet ID
  var ssName = 'Form responses' // Replace with sheet name
  var sheet = SpreadsheetApp.openById(ssID).getSheetByName(ssName);

  // Find the row where the ID in the URL equals the ID in the sheet and update the
  // status to the parameter value
  var data = sheet.getDataRange().getValues();
  for (var i=1; i < data.length; i++) {
    if (data[i][7] == responseID){
      sheet.getRange(i+1,9,1,1).setValue(status);
      var date = Utilities.formatDate(data[i][3],"NZ", "EEE, MMM d, yyyy");
      var type = data[i][4];
      var email = data[i][6];
    }
  }

  if (status == 'Approved') {
    var subject = 'Your request for time-off has been approved';
    var message = 'Your request for time-off (' + type + ') on ' + date + ' has been approved.';

  } else {
    var subject = 'Your request for time-off has been denied';
    var message = 'Your request for time-off (' + type + ') on ' + date + ' has been denied.';
  }

  // Send email to requestor alerting them of the approval/denial of request
  MailApp.sendEmail(email, subject, message);

  // Show message to manager that the response has been updated.
  var result = "The request has been '" + status + "'.";
  return ContentService.createTextOutput(result);

}