You have practiced all of your words. Try doing some lessons or translations.
In six months of duolingo I've never had this message appear, but today it's preventing me from doing my usual daily practice.
Has something changed recently?
I'm getting this message today. I've finished my tree, so have no new lessons to do.
I did have words that it said were overdue, but I don't know how to train individual words. I mostly just use "Strengthen Skills" and hope it will throw in anything I need to practice.
That worked! The home page "Strengthen Skills" exercise is by far my favourite way to use Duolingo, so I was disappointed that it wouldn't let me do it.
I should add - I've done ~10 new lessons in ~14 days, so there's plenty of words I'm not yet confident with.
Thanks Luis. I'm doing a few translations, but I don't feel ready to do more lessons until I'm more confident with the new words I've been recently shown.
I guess that Duolingo require you to give some translations back to them every now and then to keep it all going
Actually, so far as I know, Duolingo never requires that you do translations. Maybe they will in the future, but, for the time being at least, they never do. At least that is the impression I've gotten from reading some of the past forum posts made by Duolingo staff. Maybe one of them will chime in here and give the definitive answer.