[Risolto] plus buttons do not work when trying to create translated page

Background of the issue:
I am trying to create a translated version of a page using WPML. The issue can be seen at the following link: link nascosto

Symptoms:
When I click the plus button to create a new translated page, I get a blank new page with no content instead of a new page being created.

Questions:
Why does the plus button not create a translated page?
How can I fix the issue of getting a blank page when trying to create a translation?