You have a typo in your answer.
Problem #1 - Greek skills, level 3. Duolingo: Translate "the boy." Me: το αγὀρι Duolingo: You have a typo in your answer. Duolingo: το αγὀρι So my answer is the same! Problem #2 - When I click "Report a problem" I get a popup that only has one option. A check box for "the picture is wrong." The picture is fine. I don't get a chance to describe the error.
If I look really closely at what you've typed, you seem to have used an accent mark for ancient Greek: ὀ. The one for modern Greek (i.e. the one used on Duolingo) is ό. If you look carefully, you'll see the difference. When I do lesson 2 of Basics 1, the first thing I see taught is "the boy," with the translation το αγόρι.
BTW, specifying the level doesn't fix anything down. That's just a function of how many lessons / reviews you yourself have done. What can be useful is what skill something is occurring in, in this case Basics 1 I think.
There is a type of exercise where you have to select the appropriate article from a drop down list and then type just the noun without the article. If you just type the article or type the article plus drop down selection it is marked as incorrect. Could that be your problem?