“Heroes of Might and Magic V: Tribes of the East”

Hello! Can anyone help me? I have a problem – in the “One Khan, One Clan” stage, when I encounter the third clan, I can’t progress any further. On land, everything is blocked off, preventing me from reaching the fourth clan, and the same goes for the water, which is blocked by stones. I’ve explored the entire map, both on land and by sea, created a huge army, and tried every kind of magic – nothing works. In the third clan’s city, I can’t build a shipyard – it says that all the workers have left, and I can’t summon a ship from the place where I should be able to sail to the fourth clan. People, help me! What should I do? I thought maybe the disc was faulty, but I bought a licensed version and replayed the stages, reaching this “One Khan, One Clan” stage, and the same thing happens again. What should I do? Where should I go? I don’t know (((