Hello,
I agree with Pete above.
Adding more - It is also really important, when you are connecting to the Remote machine via RDP, check if you are connected via Console.
How to install or manage Symantec AntiVirus and Symantec Endpoint Protection components through Remote Desktop
http://www.symantec.com/docs/TECH104331
Secondly, Question arises Is the Communication issue being faced by only 1 machine or a number of machines? Again, If it is a Communication Issue in all, then I would recommend you to work on these Artilces below:
Symantec Endpoint Protection Manager 12.1 Communication Troubleshooting
Troubleshooting communication problems between the management server and the client
Hope that helps!!