[2020] game quits after 1 second without error, yesterday it worked fine only bought the humble dlc bundle?

How far do you get? Do you see the launcher? Do you get to the main menu of the game?

Originally posted by mp2: i see the game start as the game's icon pops up in the task bar then my security software asks if i want to allow cities skyline .exe to connect to the steam.exe when i say yes the game shuts down so it looks to me steam.exe shuts the game down? Btw i also noticed that when i entered the activation codes i accidently also activated the game again ? I was amazed that steam allowed a game to be activated twice but there wasnt an undo possible? so maybe thats why steam now shuts the game down ?

Sounds like that might be an issue with the launcher, but I'm not sure. I suggest you post on the official support forums as there are more people able to help you there.

https://forum.paradoxplaza.com/forum/forums/support-bug-reports.879/

Originally posted by mp2: totally uninstalled the game and redownloaded the lot and still it exits without any error you say its an launcher issue wich launcher the games or steam launcher? getting quite iritated by such funky programming . this is clearly a steam issue so fix it and dont send me to the game dev.

I was refering to the game's own launcher, that opens after you press Play in Steam. If you believe it is an issue with Steam, then contacting Steam Support is the way to go. I am not a Steam rep, I'm a community ambassador for Paradox, so unfortunately I am not able to help you with this. :/