I think the client disconnects and the app doesn’t saying anything.
I mostly play arena mode so this bugged happened to me more 6 times now.
Closing the client and turning it sometimes solves the problem. But mostly it is an automatic lose and it gots me frustrated.
Same here, happened 2 times during arena. The game got stuck saying its my enemy’s turn, there was no timer (rope), I waited a few minutes nothing happened, I did not receive any errors or disconnections. I could open the menu just fine and click on the environments. I forcibly closed the game after waiting for a while and re-opened it, I think it counted as a loss both times, while when it got stuck it didn’t change to “my turn”.
I think it also happened to my opponent during Tavern Brawl… game is bugged 
I think this thread is also related to the same bug:
Kil’jaeden endless turn however, I did not have Kil’jaeden - it does not seem to be related to this card at least in my games.