"you wake up at what time" is a correct idiomatic translation, too, though perhaps if you started with that in English you could also use "se lever."
I think maybe Duo sees a difference in "wake" and "get up".
I can wake up and stay in bed for another hour before getting up, for example.
"What time did you wake up?" "Seven." "Right, but what time did you get up?" "Well..... it was close to 8:30, I think"
again.. it's a guess... translating as an english person would say it or a direct translation word for word? What time do you get up at? is the way an english person would ask.
I put 'What hour are you up at' here and it was marked wrong, I was instructed to put another 'at' in front. This is a bit redundant and looks silly to a native English speaker in my opinion. I guess you could say 'At what hour are you up' and knock off the end 'at' instead but that still looks pretty clunky..
Formal writing rules hold that sentences should not end with prepositions. In speech, no one but Winston Churchill cares.
Well Churchill was slagging it, "a form of pedantry up with which I will no longer put", and the made-up rule is now thoroughly debunked and no more formal than anything else one can think of.
Weirdly it accepted "You are standing up at what time?" from me, as I only knew "debout" as meaning "standing up"...
A general response to all the comments: By this time, you should know how to play the Duolingo "game" if you want your answers to be accepted. The software doesn't accept a lot of variations. The word "at" in the various examples is completely unacceptable in correct written and spoken English.
Got counted wrong for "you are up at which time?" even though my understanding of quel/le is that it typically translates as "which (one)". Sure that may make for awkward english but that's never stopped duo before.
For fun I tried "At what time do you stand up" ? DL accepted it. Just once in a while you can win one!