"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.
nI- is a verb prefix that you put on a verb that has a third-person singular subject (they) and a second-person singular object (you).
-pu' does go on nouns as the plural suffix for beings capable of using language, but it also goes on verbs as the suffix that means "completed."
These two -pu' suffixes are not related to each other.
jIQong I sleep. I'm describing myself in a state of sleep.
jIQongpu' I slept; I have slept. I'm describing my act of sleeping after it's done.
nIQoypu''a' Did they hear you? Have they heard you? If they heard you, it's already completed, and I'm asking about that.