Check the Orc’s War in the event log by opening the scroll icon at the bottom of the screen.If you follow the instructions, you should be able to get in. I don't think you can discover a new passage unless you repeat the exploration in the cave several times.
If you've already reached the Munbury Complex dungeon, check all the icons (?) (magnifying glass) (doors) and all the passages should connect.Are you sure you are checking?
