Facebook like button. but to like what?

By default, like/share button shares the web page where you place it. If you want it to share a page of your choice, you can specify the same by selecting Custom URL in the Target URL option in the Standard Interface and Floating Interface sections at the plugin configuration page in the admin area.
If you visit the web page from Europe, you must be logged into your Facebook account in the same browser for the Facebook Like button to render. If you post the URL of the web page where you are integrating the like button, I would be able to check if there is something wrong with it.

the website is this https://www.reggiadicasertaunofficial.it/history/marbles-and-ancient-sculptures-in-the-royal-palace-of-caserta/

The perfect solution ofr me is to leave the target url as is (it shares the web page where is placed), but the like button must add a like to my facebook page. thanks

You can switch to Sassy Social Share Premium or Pro versions that allow you to create multiple instances of social share bar. For one instance you can choose only the Facebook Like button and specify the target URL of your choice and other icons will share the default URL.

ok thanks

No problem