That's right, unfortunately -- the system has difficulty finding hints for words which start with an apostrophe.
The hints are all there in the back-end system.
It's a known issue and is part of the reason why this course isn't "ready for prime time" yet -- it's only in beta for slightly more adventurous users to test.
Some of the more important words with apostrophe we mention in the tips and notes for units; others you will have to look up in your copy of The Klingon Dictionary or simply guess, get wrong, and look at the correction to see what they mean.
The word 'ej is described in the tips and notes for the second unit, "Sentences 1": https://www.duolingo.com/skill/kl/Sentences-1/tips-and-notes
Feel free to use the Duolingo wikia for any hints that can't be found: https://duolingo.fandom.com/wiki/Klingon_Skill:Basics
It's not unheard of for software bugs to cause grading problems, but I suspect a different error here. Note that this sentence does not contain any lower case L and only has upper case i.
It can be difficult to see, especially on the smaller screens of mobile devices, but the l (lower case L) has a small curl at the bottom that is absent from the I (upper case i).
As you continue to get familiar with the language, you will also start to naturally see a vowel between two consonants, since consonant clusters do not exist in Klingon. You can't have an l (lower case L) between j and q or between b and y or between y and t. Those consonants must be separated by vowels and so these must be I (uppercase i).