"You need to sleep."
It's not but for some reason only the plural is accepted as a correct answer because they can both technically have the same wording in English.
I love how I get told I have a typo when I'm translating the sentence as singular. It would be helpful if this sentence said you all need to sleep for the sake of clarity.
It would be more helpful if it just included both as accepted answers. To me, not being from the US, "you all" means "ninyi nyote", not just "ninyi".