Why is content disappearing from a child page?

Question

WordPress

Site on wp, the mystery of the year for me)))

There is a page https://www.enersport.it/corsi
it has a page child page https://www.enersport.it/corsi/test/ - when you try to go to it it is empty (it says in white that there is no content)

BUT if you go to the direct https://www.enersport.it/test/ - then there is content, what could be the reason?

Answer 1

I created a new template for the page where I indicated a banal line
the_content();

Answer 2

See how permalinks are configured Settings => Permalinks