Translation:The boy does not sleep, but the girl sleeps.
I entered, "The boy is not asleep, but the girl sleeps," and that was considered wrong. Is there something in the grammar that I am missing or is it just not entered in as an acceptable answer? In English, "the boy does not sleep" does not have the same meaning as "the boy /is/not asleep," but is there a difference in Latin?
You would use the context either of the conversation that you were having, or of the larger text that you were reading, to decide which one makes more sense as an English translation.
The Latin sentence could be either meaning, but in the absence of larger context or, say, adverbs, there is no way to be sure when you were looking at isolated Duolingo sentences like this