Cannot start the game via Steam

[RavenDark]

I do have the gearcity.exe in the installation folder (file size is 7.181.840 Bytes, MD5 CC83F778BC48301BF04DC0442F2A5CC1). I only checked the task manager to ensure it is not already running in the background when I pressed the play button.

That's why I think that I actually do have all necessary files for running the game, especially as none of the several game cache verifications I've made so far showed any missing files.