Won't Update to 1.03 - Says Game Not Installed

[RHamper]

Tried to use the update that I downloaded from Slitherine (why isn't 1.03 available at Matrix?) and it says I don't have the game installed. I do have the game installed and with all three DLCs thank you very much. All have been bought and downloaded from Matrix/Slitherine although I have done the Steam key thing.

I've tried placing the update in different directories and all the same, says the game is not installed. So, what's the issue?