Why does "Vir sum" uses an inversion to mean "I am a man" but "Ego sum puella" doesn't? Is it because of "ego"?
Latin has pretty free word order. They're all ok and should be accepted now, but unfortunately it takes some time for the changes we make in the Incubator to be active for users (sometimes as long as two weeks).
Still, please report (with the button in the lesson, not in the discussion) if it's not accepted, it's still possible something got missed!
That's also a correct (and accepted, though unfortunately the changes we've made take a while to go live) translation, but it's not the only possible one.
Well, it's at least the most normal sounding one. 'Ego' at the beginning of a sentence is extremely rare, and the SVO "ego sum x" even rarer. It technically isn't wrong, but you'll have a hard time finding "ego sum x" in any Latin texts (although I don't know about medieval and/or church Latin). Presumably the spoken language had more "ego sum x" than what was written down, but either way I don't think the course should suggest the 'technically correct but extremely rare' possibilities as the default translation.