Update II - This issue should be fixed now with latest version 1.01, but in the rare case somebody encounters this: just go to your steam folder, steamapps\common\Civitatem and run nw.exe
Update: Running Steam as administrator seems to fix this problem, but if somehow you still encounter this: run nw.exe or civitatem.exe, from your steam folder > steamapps\common\Civitatem.
At the moment some people experienced problems with relaunching the game after exiting, after a gameplay session. If you experienced this, open Task Manager (ctrl+alt+del) and kill all the process named nw.exe. Else restart steam.
This doesn't occur on the version bought from the official site, drm free.
Why this happens? Well if steam detects some processes left by your game that takes longer to close, it will think that the game is half close, but it still gonna try to run it and nothing will work, without killing the old process ...¯\_(ツ)_/¯
Sorry for this inconvenience, i am working on it, so far it with the new update, it only happens if you want to relaunch right away, without waiting some time.
Thanks for understanding,
George