The pluging front end does not advance

I installed Free Bookly correctly, but in the front end the client can’t get past the first page of the form, when clicking next it stays thinking forever and doesn’t go to the next level. I tried to send this question from my wordpress and it gave me an error. I need to see how the plug-in works before buying the pro version.

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