Feedback for XP and Level display

After playing local play for about 5 min, I exited the game. And when the next time I got back online, the ingame Overview (when holding "tab" button) displays all players as "level 0", and I cannot get any XP after the game. The situation is still the same by now. Not sure what's wrong, and if I figure out the way out, I'll get back here and share.