Ah, I see. It should accept both, I think.
(Apparently pyjamas is "mostly British", which explains why it's the version my father used and why it's not the one Duo accepted initially -- most courses use American for their English.)
Report if you prefer pyjamas and it doesn't accept those :)
You're right that in English we would usually ask a question with "Are you ..." However, to express surprise rather than ask for information (I can see that you're in pyjamas, and this is surprising) you can also use ordinary statement word order and just show the surprise/question with your voice. Duo should definitely accept both answers though!