If a Virtual Host change is made and you are using the Virtual Standby Option for a protected server then the export configuration needs to reflect the Virtual Host / Export target changes to prevent interruption in continuous exports.
Once you add the server back to protection the agent should show in the console with no previous export config displayed. Setup the export again and point to either the same datastore etc or if it had previously been completely removed allow the core to start with the new full export.
Quest does not provide support for problems that arise from improper modification of the registry. The Windows registry contains information critical to your computer and applications. Make sure you back up the registry before modifying it. For more information on the Windows Registry Editor and how to back up and restore it, refer to Microsoft Article ID 256986 “Description of the Microsoft Windows registry” at Microsoft Support.