These comments must have been entered when it was wrong. It must have beem fixed, as it is absolutely right now.
This is why it is good practice to date comments...
totally right. only when it's in a question it should have the accent. duolingo makes many mistakes in this item
I think this is supposed to be an indirect question (or an answer to an indirect question), therefore cuándo (accent). But, I also think it stands equally well as a declarative sentence, therefore cuando (no accent).