Nope, Duolingo is not sensitive to punctuation. You can skip any commas, periods or question marks you want in any language course (not only Ukr) and it will be accepted.
Please always provide your exact input. Probably you had a typo or some other mistake. It's usually displayed in the red text that pops up, pay attention to which words are underlined if any, and to the correct answer, compare it to yours.
Next time, provide the sentence you inputted in your comment :)