Hello. If you can see the campaign in the game but the missions give you an error try this.
Edit the .info file and add this line at the end:
{dependency "41e706a0-4047-42e0-810d-02f721d569bd"}
That worked for me. This line was taken from a sticky post in the mods section of the Steam page of the game.
Mati256
joined
This member has provided no bio about themself...