Ok I had a bit of a look at the logs to see whats going on when two standalone games are running.
LogOnline: STEAM: [AppId: 480] Client API initialized 1
LogSteamShared: Warning: Steam Dedicated Server API failed to initialize.
LogOnline: STEAM: [AppId: 480] Game Server API initialized 0
LogOnline: Warning: STEAM: Failed to initialize Steam, this could be due to a Steam server and client running on the same machine. Try running with -NOSTEAM on the cmdline to disable.
LogOnline: Display: STEAM: OnlineSubsystemSteam::Shutdown()
LogSteamShared: Unloading the Steam API...
LogOnline: Warning: STEAM: Steam API failed to initialize!
LogOnline: Display: STEAM: OnlineSubsystemSteam::Shutdown()
LogOnline: OSS: Unable to create OnlineSubsystem instance Steam
LogInit: WinSock: version 1.1 (2.2), MaxSocks=32767, MaxUdp=65467
LogOnline: OSS: Created online subsystem instance for: NULL
LogOnline: OSS: TryLoadSubsystemAndSetDefault: Loaded subsystem for type [NULL]
So it seems that having two users causes issues and for the Steam API to not properly initialize. Any way around it, or you just can’t test on the same machine?