Perhaps I should have added to my original comment that my answer without "wy" was marked wrong. If its optional then I'm not sure why it was incorrect unless the admins were going for the emphasis. I would imagine a Polish speaker still would understand what I was saying though...
I did flag the question that the answer should have been taken so I guess they will go from there
Well that's strange; answers with or without "Czy" are accepted, as are answers with either "wy" or "ty" (with the appropriate matching verb) or with neither pronoun (and therefore, of course, with either verb form).
I'd suggest at this point that if this happens again for you, a screenshot could be useful.