"What do you want, Mara?"
There is no such word in standard Klingon as nuqneh. The lower-case h is only used in single sounds that are written with multiple symbols: ch, gh, and tlh.
The Duolingo software gets confused by the Klingon capitalization scheme. It sometimes changes capitals to lower-case without any recognition that this officially creates "illegal" words. It also sometimes capitalizes the first word of sentences. We hope that one day the programmers will be able to find a way to stop the software from doing these things in the Klingon course. For now you just have to adjust for these irregularities when using Duolingo.