System.Exception: The server is not operational when trying to connect to GPOADMIN (4252070)

When trying to connect to GPOAdmin you receive the following error:

System.Exception: The server is not operational
at Quest.Avalanche.SnapIn.ServerNode..ctor(RootNode rootNode, String serverAddress, Int32 portNumber, String username, String password, String domain)
at Quest.Avalanche.SnapIn.RootNode.ConnectToServer(Object sender, ActionEventArgs e)

A domain controller has been removed from your environment that GPOADmin is trying to reach.

GPOADMIN tries to enumerate every DC in your environment.

It will hang if:

• A DC was improperly decommissioned/taken offline
• Service account is not an Enterprise Administrator and cannot query every DC.
• A firewall or router is blocking ports to the domain controller(s)

By default, GPOADMIN will always connect to the PDC Emulator server unless you specify via registry key.

You can force GPOADMIN to speak to a certain domain controller, which will get you past this issue.

For GPOADmin 5.9 and later:

1. From your GPOADMIN server, launch REGEDIT
2. Navigate to HKEY_LOCAL_MACHINE | SOFTWARE | Quest | GPOADMIN | SERVERCONFIG | PREFERREDDOMAINCONTROLLERS
3. Add a new  new STRING "VALUE name:" the name of the name of your domain (i.e. MyDomain.MyCompany.com) and give the "Value data:"  value the fully qualified domain name of your preferred DC. (ie. MyServer.MyDomain.MyCompany.com)
4. Confirm the DC and Domain and click Ok
5. Try reconnecting