Once you have the reset activation code and the new challenge code: On a machine with internet access, go to the Nessus Offline Registration page Enter your Challenge Code Activation Code , then click Download the nessus.license
This will output a string like: d4f5e1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8 nessus offline activation license already in use
Click on the product row to view its details. Look for the status showing the current registration. Click the button next to your activation code. Once you have the reset activation code and
"C:\Program Files\Tenable\Nessus\nessuscli.exe" fetch --register-offline nessus.license nessus offline activation license already in use
The nessuscli commands were not executed in the correct sequence, or the challenge code was misused. Step-by-Step Resolution: Resetting the License