unity3d – Agora SDK in Unity is not joining channels correctly (C#)

I am using v4.1.1 which I can\t find many examples on. This is my LoadEngine method:

public void LoadEngine(string appId, string token = null)
    {
        this.token = token;

        if (rtcEngine != null) return;

        callbackManager = new AgoraCallback();
        rtcEngine = RtcEngine.CreateAgoraRtcEngine();
        rtcEngine.Initialize(new RtcEngineContext() { appId = appId });
    }

and this is my join channel method:

public void Join(string channel)
    {
        if (rtcEngine == null) return;
        this.channel = channel;

        //Initializing Callbacks
        rtcEngine.InitEventHandler(callbackManager);
        callbackManager.OnJoinChannelSuccessCallback += OnJoinChannelSuccess;
        callbackManager.OnUserJoinedCallback += OnUserJoined;
        callbackManager.OnUserOfflineCallback += OnUserOffline;
        callbackManager.OnErrorCallback += HandleError;

        //Joining the call
        rtcEngine.EnableVideo();
        rtcEngine.JoinChannel(token, channelId: channel, uid: 0, options: new ChannelMediaOptions() { });
    }

My OnJoinChannelSuccessCallback is being called when the localUser joins the channel, but when another user joins the same channel with the same app ID and token (I have double checked these), the OnUserJoinedCallback is not called however on the other users local machine the OnJoinChannelSuccessCallback is being called.. How do I troubleshoot? How do I even know if they are actually joining the same channel?

Any help would be appreciated and let me know if you need any more information.

I have logged when the callbacks are called and I logged the UID of the local user when joining as well as the remote user when they join.. And I would obviously expect the OnUserJoinedCallback to be called when a remote user joins but that does not happen