SEP12 client not staying connected to management console

Hello,

We are implementing SEP 12.1.3 and I am seeing a problem on one of our test clients.  The client is not appearing in the client group it belongs in.  I run the Communication Update Package Deployment package on the client computer.  It then appears in the client list on the Management Console, then vanishes again. 

There is one one client doing this at this time, but I want to avoid this going forward.   

Thank you