Troubleshooting the "Nessus Offline Activation License Already in Use" error can be frustrating, especially when you are working in a secure, air-gapped environment. This specific error typically triggers when the Nessus activation code is already linked to a specific Challenge Code or Host ID in the Tenable system.
There are three primary scenarios that trigger this specific error message. Understanding which one applies to you is the key to solving it. nessus offline activation license already in use
Here is a comprehensive guide on why this happens and how to fix it. Why You See the "License Already in Use" Error Start the Nessus service: Step 2: Fetch the
You need to see the unique ID Nessus is sending to Tenable. nessus offline activation license already in use
If the problem persists after trying these steps, open a support ticket with Tenable. Provide them with your Activation Code and the output of nessus-fetch --challenge. They can manually clear the lock from their backend database.
If you still have access to the original machine, you can deactivate it locally to free up the license: Linux: /opt/nessus/sbin/nessuscli fetch --deactivate.
Windows: nessuscli.exe fetch --register-offline nessus.license Troubleshooting Tips