Ticket purchase stuck at Attendee registration

Hi,
I have an FSE website with a child theme based on Twenty Twentythree.

I have Events Calendar Pro 6.2.4 and Events Tickets Plus 5.8.1 active and registered. Woocommerce also is active and handling on-site purchases.

I created an event https://paricenter.com/tickets_buy/event/consciousness-for-real/
then I created a ticket (called “basic”)

Woocommerce has automatically created the Basic ticket product.

When I click on the Get tickets button to purchase tickets, I am taken automatically to the cart (https://paricenter.com/tickets_buy/cart) where I correctly find my tickets. If I click on Proceed to checkout (the button’ is supposed to take me to’s link address is https://paricenter.com/tickets_buy/attendee-registration/?tickets_provider=tribe_wooticket), the browser (Chrome on MacOS) tries to reach the page but can’t get there, until I get a 503 error.

Event Tickets settings:
under Payments, Enable Tickets Commerce is active;
under Attendee Registration:
I require individual attendee collection;
Attendee Registration Modal is disabled;
Attendee Registration URL slug is attendee-registration;
Attendee Registration page is set for a page called Attendee Registration (https://paricenter.com/tickets_buy/attendee-registration/) that contains the shortcode [tribe_attendee_registration]

When I try to simply open the Attendee Registration page, I get the same problem: the browser hangs until I get the 503 error. That leads me to believe that it’s the code on that page that causes the problem

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