"Did they hear you? No. They did not hear me."
Translation:nIQoy'a'? ghobe'. muQoybe'.
If it were nIQoypu''a' and muQoybe'pu' or muQoypu'be' it would be acceptable: both parties are referencing the same completed action. Having perfective on just one of them doesn't really make sense.
However, Duolingo is likely not to accept perfective Klingon translations of simple past tense English sentences, even when the simple past tense English is meant in a perfective sense. They have artificially, and somewhat inconsistently, imposed a one-to-one translation of Klingon perfective aspect and English perfect tenses, so they often don't accept good perfective translations, even when the perfective interpretation is obviously the one everybody thinks of. This example sentence is one of those cases where everybody is going to assume the perfective meaning, that they didn't hear you do a particular thing, but probably doesn't accept a perfective translation.