KF KF 1 - Uknown steam error

Hi,

I'm on it since this morning, looked on most websites and support trying to fix it without any results.

I have this "Unknown Error from steam prevented this" warning every time i want to play multi or with perks, i can't access them.

I tried :

-Cache verification
-Delete cache
-Deleting option.ini & user.ini then verification
-Deleting mutators.u & mutators.ucl then verification
-Deleting all Steams files (not folders) to force it to refresh
-Join a friends party on KF
-Uninstall / Reinstall
-Uninstall / Reinstall from another Region

I don't know what to do anymore, i'm on it for many hours, i would gladly take any help from anybody with advices or tips againts this troublesome probleme.

Thank you for your attention.

KF KF 1 - Uknown steam error