"The doctor is standing there."
Translation:Az orvos ott áll.
That's correct as well.
The difference is that Duo's sentence emphasizes "ott" (the doctor is standing there, not somewhere else), while yours emphasizes "az orvos", because that's the word directly before the verb (it's the doctor who's standing there, not someone else.)
But your sentence should be accepted as well, so if it wasn't, please report it next time.