Trying to email a PDF of a single Google Sheet

Question

I am trying to email a PDF of a single Google Sheet and have compiled the below so far. However, the recipient receives a PDF file that fails to load or even preview in Gmail.

function sendEmail(){  
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  const sheet = ss.getSheetByName('Sheet1');
  const url_base = ss.getUrl().replace(/edit$/,'');

  const url_ext = 'export?exportFormat=pdf&format=pdf'
  + '&gid=' + sheet.getSheetId();

  const opt = {
    headers: {
      'Authorization': 'Bearer ' + ScriptApp.getOAuthToken(),
    }
  };
  
  const response = UrlFetchApp.fetch(url_base + url_ext, opt);
  const blob = response.getBlob().setName('Sheet1.pdf');

  MailApp.sendEmail({
    to: 'email@address.com',
    subject: 'subject',
    htmlBody: 'body',
    attachments: blob
  });
}