confirmation page setting doesn’t work

Hi
I set a custom confirmation page in global.gotowebinar.com but there is no redirection to this page after the form is submitted

this is the thank you page:
https://www.gameffective.com/free-resources/webinars/training-session-1-simulations/thank-you/

maybe I can put this URL in the Shortcode where I see the form? I used:
[gotowebinar-reg key=”5515248575506328321″]

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