Machines which are deployed with the Symantec Management Agent installed image, cannot register with the SMP (Symantec Management Platform or Notification Server) server.
After forcing a Basic Inventory I noticed an error:
"Failed to send basic inventory, COM error: Cannot send event. The computer has not been registered on the server."
ITMS 8.x
Deployment Solution 8.x
Image contains an old Altiris agent version.
In most cases with this issue, some settings were changed on the SMP Server after image is captures. That could be IP address, name, certificates or etc.
Make sure to capture image with a new Symantec Management agent.
For already deployed machines, you can Push the Symantec Management agent from the SMP server again.