Can you provide a screenshot of this, please? (Upload it somewhere and paste the URL here.)
So that I can attach it to a bug report.
"this" and "the correct answer" are rather vague, I'm afraid, and I can't see what kind of exercise you got (multiple-choice, translate, type what you hear, fill in the blank, tapping, ....) as the system automatically generates a number of exercises from one and the same sentence.
Your sentence mildly bothered me, so I'm going to offer a correction and, if it is incorrect In grammar, atleast it'll fully translate. I assume you meant to say why is he not free, since you used "er"
The full translation is as follows: "Das ist einfach traurig. Warum ist er nicht frei?"