I am unable to do any new lessons, nor does strengthening work.
Could you provide more information so we can help you more efficiently? This is a pretty good introduction to what kinds of information is useful.
This occurred for several hours yesterday afternoon. It happened shortly after the huge glitch yesterday, and I assumed that it was possibly related to the efforts to correct that problem.
Duolingo is working now, but for your future information: 1. Each time that I clicked on the button for a new lesson, nothing happened. No dialog box appeared, and the lesson did not start. 2. Each time I clicked on strengthening, a dialog box did appear but everything was greyed out. The strength bar had the number 1 greyed out on the top right, skip in the bottom left was grey, and continue on the bottom right was also grey. Other than that, there was nothing else on the page. No questions, and clicking on the greyed out buttons had no effect.