If you plan to decommission a server, always run nessuscli fix --reset or nessuscli fetch --unlink while it still has connectivity, or manually release the key in the Tenable portal immediately during the teardown phase.
Paste your (License Key) into the second box. Click Submit . The portal will now successfully generate two items:
Open the Command Prompt as an Administrator and navigate to the Nessus directory:
Now, return to your offline Nessus machine to apply the fresh license and load the vulnerability signatures. 1. Register the License File
If you are decomissioning a Nessus VM, always run nessuscli fix --reset before destroying the machine. This helps gracefully release the seat. nessus offline activation license already in use
After successful validation, the portal will provide:
Prevention and operational best practices
If you previously activated a license on a computer that had a hardware failure or was decommissioned without properly removing the license, that license can still appear as "active" in Tenable's system. This prevents you from reusing it on a new or rebuilt system.
Immediate remediation steps (ordered, actionable) If you plan to decommission a server, always
/opt/nessus/sbin/nessuscli fetch --register-offline nessus.license Use code with caution. Step 5: Update Your Plugins
Install the Nessus package on your air-gapped system without completing the online registration process.
: On an internet-connected machine, go to the Nessus Offline Registration page .
This error occurs because Tenable's activation server recognizes that your specific activation code is already linked to an active Nessus installation. To resolve this, you must clear the old registration before the system will allow a new offline activation file to be generated. Why This Error Happens The portal will now successfully generate two items:
Look for a button or link labeled , Deregister , or Unlink .
To avoid ever seeing "license already in use" again, implement these three policies:
Download both files to a secure flash drive or transfer medium to move them to your air-gapped Nessus host. Step 5: Apply the License and Plugins Offiline