Echoes of War

It says that the map is missing or corrupted. I don't have any mods.

Did you copy the files correctly? You should only copy files from a single archive.
Try opening the maps in the editor.
Try running individual scenarios, not through the campaign.

In general, it's very strange that these problems are occurring. The campaign is not a mod.
It would be great if those who have the campaign working could respond.
It can't be working only for three people!)