Book Tour issue

I have a somewhat custom tour (called Transfers) which is basically an airport transfer service.
When click the add to cart button, instead of adding to cart and redirect to the checkout page, it gives me a page not found error.
Also, the following JS error is present when clicking the button:

Uncaught TypeError: _product_form_variations.forEach is not a function
at HTMLButtonElement.<anonymous> (c79e7636c2800e42127ce9dec2ed51a6.js:1005)
at HTMLDocument.dispatch (jquery-1.12.4.js:3)
at HTMLDocument.r.handle (jquery-1.12.4.js:3)

You can see for yourself on the developer tools.

The page in question is:

https://t3tours.pt/product/faro-airport-transfers/

Any idea what’s wrong?