NetworkManager how StartMatchMaker works? ListMatches not getting my server.

Hello everybody, this should be an easy question.

I have a simple menu and when a player press the button "Play" it calls the following code.

    public void OnClickPlay()
     {

         lobbyManager.StartMatchMaker ();
         lobbyManager.matchMaker.ListMatches(0, 1, "", OnMatchList);
     }

Where lobbyManager is the name of my Networkmanager class ( it extends the class)

Everything was working perfectly until today and I haven't done any changes to it. Now whenever I press the play button and run the snipped above it returns me the log

JSON Response: [[UnityEngine.Networking.Match.ListMatchResponse]-success:True-extendedInfo:]-matches.Count:0 UnityEngine.Networking.Match.c__Iterator0`1:MoveNext()

And I cant see the other players on the same room, it seems like unity cant find the server and always creates a new one instead of connecting.

Any Idea how to solve this or a hint??

Thanks a lot,