Please be careful on your placement of the ' symbol, it is a letter of the Klingon alphabet and misplacing it is misspelling the word.
The software is incapable of displaying the hints for Klingon words that begin with the ' letter. Hopefully one day they will fix that.
For a list of known issues in this course, read the post at: https://forum.duolingo.com/comment/26778885
The only way I know of to complain to the administration about the fact that this had still not been fixed is to file a bug report: https://support.duolingo.com/hc/en-us/articles/204728264-How-do-I-report-a-bug-
For the first part of the course we provide the definitions of words that begin with the ' letter in the Tips & Notes.
Since Duolingo has hidden the Tips & Notes I want to make sure you know about them and where to find them. If you have not been reading the Tips & Notes, I would like to ask that you review those so we don’t have to continuously repeat the information that we have explained there.
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 Start button, a key, and a light bulb.
If you click on the light bulb it will reveal the Tips & Notes and give you a detailed explanation of the grammar that is introduced in that Skill. If you have questions after reading the Tips & Notes for any Skills, then please return to the forum to ask your question, explaining what you didn’t understand or what seems contradictory to you.