Always run the following before wiping a scanner:
The terminal will print a string of alphanumeric characters (the ) along with an offline registration URL. Copy this challenge code exactly and save it to a text document or flash drive. Step 3: Download the New License File and Plugin Feed
Marcus sat back, the plastic chair groaning under the weight of the revelation. The Nessus instance was not a vulnerability scanner anymore. It was a sentinel. A testament to a woman who had known she would be erased, so she had built a machine that could not be silenced—only ever told, “Your license is already in use.”
This error is rarely a sign of a technical glitch; it's usually the expected result of several common scenarios:
Tenable imposes a transfer limit on licenses. You are typically allowed to deactivate and reactivate your Nessus Professional license only a limited number of times within a certain period, often a 90-day window [13†L38-L40]. If you exceed this limit, the license may be temporarily locked or frozen, requiring manual intervention from Tenable Support to enable further changes. nessus offline activation license already in use full
The activation code status will change back to "Available." It is now ready to link to your new offline machine footprint. Step 2: Generate a New Challenge Code
When you encounter this error during an offline setup, the fastest fix is to log into your Tenable account reset the activation code
Nessus 8.7.1. CLI active. Last scan: .
Elias had done everything by the book. He’d generated the Challenge Code from the isolated scanner, walked the USB drive across the "air gap" to his workstation, and logged into the Tenable portal. He had the license key. He had the activation file. But when he tried to marry the two, the system balked. Always run the following before wiping a scanner:
: After clicking submit, scroll to the bottom of the page to download the nessus.license file. 4. Apply the License to the Offline Scanner
The "Nessus offline activation license already in use" error occurs when a Tenable Nessus activation code is tied to an active machine profile or an old installation challenge key. This prevents administrators from generating a valid nessus.license file or finalizing air-gapped system registrations. This error is common during server migrations, hardware reconfigurations, or clean re-installations in secure environments.
Once completed, restart the Nessus service to force it to process the new license and compile the new plugins:
If you attempt to:
Yes , he thought. And it always will be.
: Run the command /opt/nessus/sbin/nessuscli fetch --challenge (Linux) or nessuscli.exe fetch --challenge (Windows) on the offline machine.
| Cause | Explanation | |-------|-------------| | | Reinstalling the OS or Nessus without deactivating first creates a new fingerprint, but the old one remains registered. | | VM cloning | Cloning a Nessus-enabled VM duplicates the configuration, but Tenable sees the clone as a new machine. Both original and clone try to use same license. | | Changing major OS version | Upgrading from CentOS 7 to Rocky Linux 8 changes system UUID, triggering a new activation request. | | Hardware change | Replacing a network card, motherboard, or CPU can alter the system identifier. | | Trial license expiration & reactivation | Free trials allow 1 activation only. If you previously activated offline, you cannot do it again without Tenable resetting your key. | | Manual license reuse | Trying to use a license file (.lic) generated for a different machine ID. |
Open a web browser on a device with internet access and navigate to the Tenable Community Portal. Log in using your registered account credentials. The Nessus instance was not a vulnerability scanner anymore