Anyone else got an issue with the Idiom supplmentary skill?
Well, not the skill per se, but no matter how much I train it, it doesn't show as gold on mobile (it does on the desktop version). It's my OCD talking maybe, but it's annoying to have that blotch on my otherwise golden tree. Also make it harder to know when it needs to be trained.
I don't know if this comment would be helpful. In my case, I have the Idiom Supplementary Skill for Italian. I use mobile and desktop modes (IOS). Haven't had any issues with it. When it loses bars I am able to go back to lessons and it does turn golden. As 1Neutrino suggested, rebooting helps. I find it amazing how many tech issues are resolved just by rebooting when one hasn't restarted or shut-down device(s) for a while. Good luck!