Nessus Offline Activation License Already In Use Here

You uninstalled Nessus and tried to reinstall it on the same machine, but the server didn't "release" the old hardware ID.

If running Nessus in a VM, set a static MAC address. If the MAC address changes, the Challenge Code changes, and your license will break. nessus offline activation license already in use

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. You uninstalled Nessus and tried to reinstall it

Locate the Nessus activation code that is giving you trouble. Look for a "Reset" or "Unlink" button next to the license. Look for a "Reset" or "Unlink" button next to the license

Open your terminal and run: /opt/nessus/sbin/nessuscli fetch --challenge

Moving a Nessus VM to a new host often changes the hardware UUID, triggering a license mismatch. Step 1: Reset the Activation Code

If you changed the network interface card (NIC), CPU, or hostname, the Challenge Code changes, making Tenable think it's a new device.