I have played more than 200 challenges in last evening but SoloLearn counted only 60 for all day. I noticed such issues during last 10 days. Especially completed challenges initialized from my side didn't count.
I faced the same issue for a couple of weeks already... Anyway, it just seems to be a daily XP issue. Might be a motivational thing. Otherwise the same guys and girls are the daily champs all the time... Why not let some newbies be the daily champions? 🤔