What is wrong with LINGQ on iPad and iPhone?

This morning I still used Lingq on my iPhone. No problem. But now, all of a sudden, Lingq disappears when i click on the app: I see the Lingq screen during a tenth of a second, then it disappears in a flash. This happens on my iPad as well as on my iPhone. I tried to re-install Lingq, but got the same problem. What can be wrong?

OK, 10 minutes later it works again as usual. I don’t know what was the problem.