Wcf service not pushing the updates to client

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WCF

C#7.0

I have a WCF service, every 30 seconds it pushes the status to connected clients
my service code here:

private void StartStatusPushing(int callBackInterval)
        {
            Task.Factory.StartNew(
                () =>
                {                    
                    while (true)
                    {
                        Thread.Sleep(callBackInterval);
                        // come code here.
                    }
                },
                TaskCreationOptions.LongRunning);
        }

I have a client application and get the status every 30 seconds via callback channel.

I have a problem like this:
1. At first time started the service and started the client
2. service pushing the updates and client receiving the updates.
3. Then i closed the client and start again without closing the service
4. Then service is not pushing anymore (generally after x second the publish method should run).

so how resolve the issues.

What I have tried:

previously I have a one client application, but now I have 2 application so both should get the updates