When you perform an offline activation, Nessus generates a challenge code based on your machine's unique hardware signature. Tenable uses this to generate a license file that is married to that specific machine.
You will encounter the "License Already in Use" error in two main scenarios: nessus offline activation license already in use full
If you have access to the Tenable Support Portal (even via a separate internet-connected machine), you can release the license yourself. When you perform an offline activation , Nessus
A: You cannot deactivate an offline scanner remotely. Instead, use the Tenable portal to deactivate it manually by selecting the entry and clicking "Deactivate" – this work even if the scanner is offline forever. If you have access to the Tenable Support