So you reached the camp in front of Enderal, then you went to sleep and got woken up by the war drums.
Then you went up the wall to watch what is going on and got the info that Enderal is attacking. (then happens the bit with the fire balls ^^)
The castle meant is the camp with the stone wall and the gate

You just need to walk a bit in front of the gate and it should update once more. (if it doesn't update try walking a bit around in that place, sometimes the trigger is a bit buggy and needs you to walk in the whole perimeter to work ^^