I hoped that the audio would get people to realize that Klingons don't say JLYLN, but someone just now reported "Does not recognize correct answer of jlyln."
By now I've come to realize that in user reports, "I typed in the correct answer but it marked it wrong," really means "I typed lower case L instead of capital i," but I appreciate the clarity of this report. The l/I distinction is the first adversary in the battle to learn Klingon, but one that is easily vanquished.
An explanation is given in the Tips & Notes, but Duolingo has hidden the Tips & Notes. If you have not been reading the Tips & Notes, I would like to ask that you review those.
If you are doing the course on iOS or Android, you cannot currently access the Tips & Notes through the app. To access the Tips & Notes, you will have to access the course using a web browser at https://www.duolingo.com/. You can still do it on your mobile device, but you will have to use the web browser instead of the app (or you can do it from a computer). When you click on a Skill, it will expand to reveal a large Start button and a large Tips button.
If you click on the Tips button it will reveal the Tips & Notes and give you a detailed explanation of the grammar that is introduced in that Skill. If you are on the web interface and see neither a lightbulb, nor a "Tips" button, then that specific Skill probably doesn't have any Tips & Notes.
If you have questions after reading the Tips & Notes for any Skills, we are happy to answer your questions, but many of your questions will probably already be answered in the Tips & Notes.