If the User ID used to register a managed product is deleted, all the products that you registered under this account will not be able to re-register or unregister themselves from the Control Manager server.
Agents re-register themselves when their services are re-started or when they detect that their records on the Control Manager database are either missing, or not current.
Unregistration occurs when the agent is removed from the server of the managed product. If the agent is unable to unregister itself, its remains on the Product Directory.
See also:
Recover managed products removed from the Product Directory