If you've verified that your license key is correct and not in use elsewhere, but still encounter the error, it's time to contact Tenable Support. Provide them with:

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

You built a Nessus scanner in a virtual environment (VMware/Hyper-V). You activated it offline successfully. Later, you cloned that VM to create a backup or a second scanner. Because the clone retains the original MAC address and UUID, the remains identical.

On your , you must generate a unique "Challenge Code" that links your hardware to the activation key.

: Find your Nessus Professional license and click Manage Product .

C:\Program Files\Tenable\Nessus\nessuscli.exe fetch --challenge macOS: /Library/Nessus/run/sbin/nessuscli fetch --challenge Copy the alphanumeric string provided. 3. Obtain the license file

With a reset license and a new Challenge Code, you can now generate the license file. Go to the . Enter your Activation Code (the one you just reset). Paste your New Challenge Code . Click Submit and download the nessus.license file. Copy this file to your offline machine. Step 4: Apply the License and Plugins