"Kronos is the Klingon homeworld."
Translation:tlhIngan juHqo' 'oH Qo'noS'e'.
Using the report flag wouldn't have accomplished anything in any case. That sounds like a software bug and the contributors can't do anything about those. Did you take a screen shot? You could send a screen shot to https://support.duolingo.com/hc/en-us/articles/204728264-How-do-I-report-a-bug- and the programmers could see if they can track down the problem.
Actually the mistake was ours -- probably mine -- with an acceptable Klingon answer accidentally typed into the English answer field. I have corrected it, and thanks for the report. It's actually way better if you come here to report problems, because that way you can explain clearly and thoroughly, and we can respond to you and ask follow-up questions.
We find the reporting forms pretty annoying too, and the interface for finding and dealing with them is not great.