Fire Javascript not working…

Hello,

I am try using Fire Javascript with last version of contact form 7 and not it is working…

I am using ext script:

document.addEventListener( 'wpcf7mailsent', function( event ) {

        dataLayer.push({

          'event' : 'wpcf7successfulsubmit',

          'formId': event.detail.contactFormId

  })

 });

should fire this event every time the form is submitted but it does not.