Backup, Restore, or Clone your PMS installation
Do not copy the preferences.xml from the existing server.
Even though you removed the claiming information, it still has the information that uniquely identifies the server to Plex (MachineID, etc.).
On the new server:
Stop PMS.
Rename preferences.xml to preferences.xml.old
Start PMS.
Plex will create a new preferences.xml.
Then try and claim the server.
You can also use the User Credential Reset utility to claim the server.
