I can't join the cs

No When I try to subscribe, this window appears. I unsubscribed the content and it dont work

 

Then you have from some item an update (e.g. skinpack etc.) installed which blocks the installation of the cs mod.
You need to check your content and uninstall them.

 

Is there a way to know which item causes the conflict?

 

No. You can just check the required content cars + tracks and search in the content manager. But there is sadly no support from the game.