Hi!
I've got the same problem. Trying to start the first mission, and nothing happens. The game just returns me back to the main menu.

Please, help to fix it :)

You have to download all he requirements on the same mod page first. I had the same problem until I worked out why

Tried everything as well. All mods are downloaded, they're in the correct folder and the game recognizes them all, they all have the _1 suffix, I have a profile.lua that has all campaign missions completed. Seems like this particular mod has an issue with being stored in the user directory as this game does if bought from GOG.