I need to make an alternate language available for a subsite (S) of a site collection but, when I open the 'site settings' page of S, the "language settings" voice (in the "Site Administration" section) is not showing. The voice is not showing in the site settings page of the parent site collection either.
In other web applications belonging to the same farm, this does not happen and the voice is showing as expected (see pictures below, where "impostazioni lingua" is italian for "language settings").
Why does this happen?
What do I have to do to solve this problem?