"Mara walked from the Great Hall to her home."
Translation:vaS'a'vo' juHDajDaq yIt mara.
Your use of the word "successfully" makes me wonder if you are actually thinking of the suffix -ta'. In any case, you are not altogether wrong. Depending on the context it might be very appropriate to use one of the perfective suffixes in a sentence like this. However, because Duolingo does not give us an opportunity to indicate a context. In this course we consistently translate the perfective aspects with the English perfect tenses, even though the correlation is not 100%. Similarly we translate the lack of the perfective suffixes with the simple tenses.
Aside from "successfully," as jdmcowan points out, you are correct. vaS'a'vo' juHDajDaq yItpu' mara means that Mara completes a walk. The given sentence, vaS'a'vo' juHDajDaq yIt mara means Mara takes a walk, but we are being told about the walk in a context in which it's not a completed event.
It's a bit like the difference in English between I walked home (a completed event) and I walked every day (this isn't a completed event; it's a statement of my habit of walking). English doesn't mark the verb for this distinction; you have to figure it out from context. Klingon explicitly marks the completed version with -pu' or -ta', and lacking an aspect suffix means the action is not completed or continuous.
Unfortunately, you'll find a lot of confusing examples like this in the course, because the authors didn't really quite get that Klingon perfective doesn't equal English perfective tense, and that verbs not marked for aspect can't represent completed or continuous actions. (Because, let's face it, the author of this sentence was thinking of a single, completed walk home, not a statement of Mara's itinerary.) It's not a concept that comes easily to the English native's mind.