[Risolto] Problems with newly create language not displaying

Background of the issue:
We have created 'American' language for our client on link nascosto, and on testsite link nascosto. We are writing to you from a different account to get support. The problem is on the live site - link nascosto, where 'American' is only displaying on frontend language selection. The alias domain - link nascosto is displaying the content correctly, but the language selection is not. On the testsite - link nascosto - where languages have been set up as subfolders, it's all working correctly.

Symptoms:
'American' language is only displaying on frontend language selection on the live site, but the alias domain is displaying the content correctly. The test site works correctly with languages set up as subfolders.

Questions:
Can you see where the problem is to solve this, since we cannot find the issue?