/opt/nessus/sbin/nessuscli fetch --challenge If this returns nothing or an error, the instance is not activated. Try deactivating the current (old) instance if it still exists:
Here’s a deep, technical review of the error — covering its root causes, impact, troubleshooting steps, and long-term prevention. 1. What the error actually means When Tenable’s Nessus scanner reports “license already in use” , it means the activation code (license key) you’re trying to use is already linked to an active Nessus instance registered with Tenable’s licensing servers. nessus license already in use
Would you like a template for contacting Tenable Support to expedite the license release? What the error actually means When Tenable’s Nessus
If old instance exists → deregister it → reactivate new one. If old instance is dead → contact Tenable Support with proof of license ownership. If old instance is dead → contact Tenable