User blog comment:KodachiZero/We finally have an Admin!/@comment-121.54.54.136-20140404080440/@comment-112.208.31.143-20140404091714

The reason your arena orbs aren't refilling is that (maybe) you closed the app before you lost an arena match. If this happens, the only way is get them to refill again is to win an arena match, level up, or spend a gem.