May I suggest "why aren't you all resting?" as an accepted answer? I realize it's challenging to capture all of the colloquial ways to record 2nd person plural in English, and maybe the Southern US "y'all" is too regional, but i think it might help learners to have some options for translating ξεκουράζεστε as both formal and plural 2nd pers. Just a suggestion and thanks to all of you outstanding mods who read and help develop this program!
This is actually something the Italian course does, which can be pretty helpful. It's obviously not necessary, and we haven't done/haven't been doing that in the 2nd tree either. We usually include both forms (2nd person singular and plural) in the hints so that users are reminded of both. Thank you for your input and kind words :)
I could see that report but it was highlighted in green (indicating that that sentence should have been accepted), so I'm not sure what went wrong.
Perhaps that sentence had been explicitly rejected at some point and that rejection overrides the fact that that sentence is in the list of accepted alternatives.
I'll see if I can find that.
Edit: I can't find a rejection by searching for the sentence or the translation, but the tool I used is a bit finicky.