[Chiuso] Automatic translation is not working

Background of the issue:
I am trying to automatically translate the content in the Advanced Translation Editor, but the content is not getting translated.

Symptoms:
When translating all content on the page: nothing happens. When translating single content items, I get the content in the original language.

Questions:
Why is the automatic translation not working in the Advanced Translation Editor?
How can I ensure the content gets translated automatically?