Customer service MIA

My daughter is studying a new language and her app is stuck on a lesson no matter how many times she completes it. I've restarted the app, restarted the iPad, deleted and reinstalled the app, etc - with no luck. I set it up for her through an Apple subscription so there isn't a login for her to use it on a browser.

I've tried for a week to reach Duolingo CS without any reply.

My daughter is a studious learner and cries every night that she can't do it. Any advice?