nessuscli fetch --deactivate

/opt/nessus/sbin/nessuscli fix --deactivate

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Setting up Tenable Nessus in an air-gapped or secure environment requires an offline activation process. This method relies on a challenge string generated by your scanner and an activation code from your Tenable portfolio. However, users frequently encounter a frustrating roadblock during this process: the error.

: Run the command /opt/nessus/sbin/nessuscli fetch --challenge (Linux) or nessuscli.exe fetch --challenge (Windows) on the offline machine.

However, a notoriously frustrating error can appear during this process: (sometimes truncated as "License already in use" or "Activation limit reached" ).

To free up the license for your new offline installation, you must reset it through the Tenable Community portal:

This action clears out the old machine fingerprint on Tenable's backend without changing your actual alphanumeric activation code string. The license is now freed and ready for a brand-new registration challenge. Step 2: Generate a Fresh Challenge Key on the Target System