On UTC September 23th, 2016, at 1:00 an update was released.
If the game doesn’t have the newest data it won’t run properly.
If you were playing at the time of release, please go back to the title screen to update the game.

Update Notes

The quest “Front and Back Stage” from the Story Dungeon’s chapter 8 has been released!

Announcement page:
https://www.happydungeons.net/news/update/391/