StartSingleplayer seems to not work

I had a long break of gamedev, now i'm trying to use the lobby sample with a singleplayer option instead of the randomjoin button.

i replaced the randomjoin button with singleplayer, but it keeps hanging and doesnt load anything.
could someone tell me why this is?

thanks in advance

attaching a screenshot also.
https://ibb.co/xLZsFdF


the code: lobbymanager.cs
private void StartServerEventHandler(string matchName)
{
this.matchName = matchName;
BoltLauncher.StartServer();
}

private void StartClientEventHandler(bool randomJoin = false)
{
this.randomJoin = randomJoin;
BoltLauncher.StartClient();
}

private void StartSinglePlayerEventHandler()
{
BoltLauncher.StartSinglePlayer(); // somehow this doesnt work //falcon
}

///////////// lobbymanager.UI.cs
private void StartServerEvent()
{
uiInfoPanel.Display("Creating Room...");
StartServerEventHandler(uiMainMenu.MatchName);
}

private void StartClientEvent()
{
uiInfoPanel.Display("Connecting to Cloud...");
StartClientEventHandler();
}

private void StartClientSingleplayerEvent() // replaced random to use singleplayer //falcon
{
uiInfoPanel.Display("Starting Singleplayer...");
StartSinglePlayerEventHandler();
}
/////////// lobbymanager.UI.cs
uiMainMenu.OnCreateButtonClick += StartServerEvent;
uiMainMenu.OnBrowseServerClick += StartClientEvent;
uiMainMenu.OnSingleplayerClick += StartClientSingleplayerEvent;