addEventListener wpcf7mailsent never fires

Hi,

I need to add some very simple event listener code to the contact form on this (demo) page:
https://askan.co.il/testing-contact/
I copied the code from https://contactform7.com/dom-events/ but the wpcf7mailsent event never fires. Other javascript and jquery code on the page works fine, but this not at all. I spent *hours* trying to get this to work, and am getting nowhere. I would really appreciate your assistance here!

Thanks much!

The page I need help with: [log in to see the link]