We currently are working on a fix for a bug that results in player XP and fighter XP not displaying correctly and sometimes causes the game to crash. For some players it crashes after each fight and I've seen at least one other report of a player not being able to load the game either.
As far as we can tell, this issue is caused by the device being set to a language other than English. If that's the case for you as well, will you try setting your Device to English (if it isn't already) and see if the game loads?