Steamworks.SteamApps.OnNewLaunchParameters is never called because the events are not registered in SteamApps.

SteamApps has an InstallEvents method but it is never called. I managed to fix this in my own project by calling SteamApps::InstallEvents via reflection.

To reproduce:
Hook up a some code to the SteamApps::OnNewLaunchParameters callback
Launch the game
Run steam://run/<AppID>//+some,arguments
The code in the callback is not run