I had that problem. Cleared my cache and it disappeared. Sometimes the "stock" answer is the right one.Cannot fight in GbG. Says internal error restart needed.
Although apparently it was just a temporary fix. Problem is back. Only on one world out of 12 I play, though. (The bad part is one of my DC tasks today is "Win 4 battles". Usually a piece of cake in this world.)I had that problem. Cleared my cache and it disappeared. Sometimes the "stock" answer is the right one.