On Android, in Sentence Mode, only since very recently, ‘Show Translation’ sometimes doesn’t work. It just says ‘downloading’, but never downloads. See screenshot below.
If, however, I open the same lesson on the browser and use ‘Show Translation’, it works fine.
This is the lesson I was using, but it happens with other lessons in this course too (I haven’t ran into it on other courses yet though): Login - LingQ