I was surprised to see my translation "Are you in work?" flagged as wrong with the comment "This translation does not sound natural in English." I'm wondering whether this is a British / US English thing. The use of "in work" to mean employed, is very common in British English. A Google search for "Are you in work" brings up 337,000 hits but certainly the first few pages of results using the phrase in that sense seem to be for UK sites.
There are some minor differences between US and British English use of prepositions that I am aware of, e.g:
"On the weekend" (US) - "At the weekend" (British)
"On Madison Avenue" (US) - "In Park Lane" (British)
In my brief experience with it so far, Duolingo has been very responsive to British English translation suggestions, so I'm not so much complaining about the rejection as expressing an interest in whether the usage of "in work" to mean "employed" is indeed not seen in US English. Would any Americans like to comment?
I'd guessed it was something like that, and I can appreciate how dealing with English variants, including of course our minor differences in spelling, could be a delicate issue for Duolingo and for English learners.
When we come across a usage not in our native variant it's usually immediately apparent although very occasionally we fail to notice and can be misled, but it's much harder to spot the absence of one's own usage in the other's variant. I remember a "Letter from America" radio talk by the late Alistair Cooke in which he admitted that he had always failed to understand the slight confusion he regularly provoked by asking for soda water. After some 30 years he learned to ask for club soda instead, and grocery shopping instantly became easier.
As Oscar Wilde wrote in The Canterville Ghost, "... we have really everything in common with America nowadays, except, of course, language."