If you still have access to the original host, you can cleanly release the license using the Nessus Command Line Reference .
The error (often appearing as "Code in Use") typically occurs when you attempt to activate a Tenable Nessus instance with an activation code that is currently registered to another system. Because Tenable Nessus licenses are generally limited to one active scanner at a time , you must release the code from its previous assignment before it can be reused on a new installation. Common Causes of License Lockout nessus license already in use
/opt/nessus/sbin/nessuscli fetch --challenge If you still have access to the original
If you are using an older version of Nessus Professional or can’t find the "Unlink" button in your portal view, you need to get Tenable Support involved. nessus license already in use
To avoid this headache in the future, always perform a before wiping a machine.
# Windows C:\Program Files\Tenable\Nessus\nessus-fetch.exe --register <YOUR_CODE>
Support can manually deregister the orphaned instance.