Unable to join game when app is not already open

[Hugo5503]

I am trying to setup the "join game" feature via friends list while the client has the game closed.
When the client has his game open and clicks "Join game" he is succesfully added to the hosts game so this feature works and makes use of the OnGameRichPresenceJoinRequested function.
But when I click Join game while the client has the game closed, the app launches but the client is never started.

I have stumbled across multiple ideas of how it should work but can't seem to connect the dots.
I should be able to retrieve the launch option in the start function?
Using this code but it keeps returning empty strings.
var test = SteamApps.GetLaunchParam("+OnConnectLobby");
But should I also set this code? And if so how? I would expect in the OnLobbyCreated maybe like this?
lobby.SetData("+OnConnectLobby", SteamApps.AppOwner.ToString());
But that does not seem to work.

Other options I came across is to work with SetRichPresence but I think I am just confusing multiple concepts here based on the api documentation of steamworks.

Can somebody point me in the right direction?

[Hugo5503]

What I ended up doing for now is getting the launch parameters using the line: var commandLineArgs = Environment.GetCommandLineArgs(); so not using the API provided. I think I will get in trouble later wen I am going to implement richPresence but I am not sure yet. Hope somebody will see this and help me out, or find this comment usefull.

Also discovered that you can see the launchParameters using taskManager by going to processes right clicking a column text and selecting "Command line" whenever my game gets launched via steam friend list you can see the given parameter.

var commandLineArgs = Environment.GetCommandLineArgs();
var connectLobbyIndex = Array.IndexOf(commandLineArgs, "+connect_lobby");
ulong lobbyId = 0;
if (connectLobbyIndex != -1)
{
    var nrOfParameters = commandLineArgs.Count();
    if (nrOfParameters > connectLobbyIndex)
    {
        Debug.Log($"NrOfParameters {nrOfParameters}");
        var unparsedCommandLineArgs = commandLineArgs[connectLobbyIndex + 1];
        Debug.Log($"unparsedCommandLineArgs {unparsedCommandLineArgs}");

        lobbyId = Convert.ToUInt64(unparsedCommandLineArgs);
    }