"Livia is not a man."
Translation:Livia non est vir.
Too much emphasis on word order that doesn't exist in actual Latin texts. Livia vir es non, and all variations should be accepted.
We are working on adding them. Bear in mind that the course has barely been out and so a lot of things will be missing, the best way to help get them fixed as quickly as possible is to use the report button in the lesson (and not comment about the answer in the discussion unless there are questions about whether or not it's acceptable). Also be aware that unfortunately the changes we make don't show for users right away, sometimes it takes up to two weeks (though it's usually faster than that).
Having said all that, the verb should be "est", not "es".
The course is in beta, they are slowing adding the variations. If you try a word order that is not accepted by Duo and you think it should be, flag it so the contributors can see it. I am sure that will help them get all the variations added much quicker.