available slot link not working

In my booking form, people can book a free appointment per half hour on Mondays. It all looks the way I want it, but the link doesn’t work when you click on a time slot: the page is refreshed and no appointment is shown in the calendar. What wouldn’t I have put right? I also disabled the CookieYes plug-in because I suspected it was causing a problem, but that turned out not to be the solution. I checked the demo and the settings all seem to be good.
Thanks in advance for your help!!!

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