if its showing the other lobbies then its a configuration error, the steam Appid 480 server has been having issues for a couple months and being up and down though.
Below is a working config (assuming you have enabled the steam sockets plugin)
[/Script/Engine.GameEngine]
!NetDriverDefinitions=ClearArray
+NetDriverDefinitions=(DefName="GameNetDriver",DriverClassName="/Script/SteamSockets.SteamSocketsNetDriver",DriverClassNameFallback="OnlineSubsystemUtils.IpNetDriver")
[/Script/OnlineSubsystemSteam.SteamNetDriver]
NetConnectionClassName=“/Scripts/SteamSockets.SteamSocketsNetConnection”
[OnlineSubsystem]
bHasVoiceEnabled=true
DefaultPlatformService=Steam
[OnlineSubsystemSteam]
bEnabled=True
bUseSteamNetworking=True
SteamDevAppId=480