[Risolto] I am trying to duplicate everything for other variants of English language only posts on my site htt...

Background of the issue:
I am trying to duplicate everything for other variants of English language only posts on my site link nascosto. Some pages have been duplicated, but I am unable to duplicate others such as the menu and everything else. When I have duplicated, for example, the homepage, I get an error and I also have an issue with the slug which I would like to be link nascosto.

Symptoms:
Unable to duplicate the menu and other content using WPML. Error occurs when duplicating the homepage. Issue with the slug.

Questions:
Why am I unable to duplicate the menu and other content using WPML?
What steps should I follow to ensure all content is duplicated correctly for other English language variants?