Hello, the solution I found was to create a new Checkout or Complete Purchase page and put the Woocommerce shortcode, and then mark it as the checkout page in the Woocommerce options.
The shortcode returns the real Woocommerce form and you can now use hooks and plugins to modify the fields.
Thank you very much, I am closing the post because I no longer have the problem, although it is strange that by default the real Woocommerce fields do not appear on the Checkout page.
