[QUESTIONS and ANSWERS] Walkthroughs for the Heroes 3: RoE, AB, and SoD campaigns.

Neither this, nor the attempt to move it to the town, was successful... The map is completely empty, and the mission doesn't complete.

Then I don't know. I played a long time ago, but I definitely remember that I didn't have any problems with this map. Try replaying, installing a newer patch, or finding a different version of the game. I don't think there's anything else you can do.