I unlocked quest mode and wanted to try it. Regardless of which party I take (I've tried different ones, both with default starter decks and manually tweaked ones), when I try to play a scenario (also regardless of difficulty), I get the loading screen, the music fades out, and it stays stuck that way, leaving me only to quit and restart the app.
I'm playing on an iPad 4 with iOS 9.3.1.
I don't know if this is related, but I also have the issue some people (including myself) already reported in another thread of having gold reset to 0 and earning no further gold and all store items costing -1 gold. I am however quite certain I already had the 0 gold earning issue before I restarted the app because it was stuck loading into quest mode, since I believe I unlocked quest mode after beating The Poison Pill, and I already earnt 0 gold for that.