Once you have a new .lic file, apply it manually.
To avoid future issues:
From a user experience (UX) perspective, this error is a failure of design for several reasons:
Blog Post: Troubleshooting "License Already in Use" During Nessus Offline Activation
If you've ever tried to set up Tenable Nessus in a secure, air-gapped environment, you know the offline activation process is your only lifeline. But nothing halts a security audit faster than the dreaded error: "Activation Code Already in Use."
This happens because a Nessus activation code can only be registered to one host at a time. If you’re reinstalling Nessus or moving it to a new offline machine, the Tenable registration server still thinks your license is tied to the old hardware.
Here is how to reclaim your license and get back to scanning. 1. Reset Your Activation Code
Since your scanner is offline, it can’t tell Tenable’s servers to "let go" of the license. You must manually release it through the Tenable Support Portal or the Tenable Community.
Login: Access the portal from a machine with internet access.
Locate Products: Navigate to "My Products" or "Products and Activation Codes".
Reset: Find your Nessus Professional or Expert code. If it’s assigned to a host, click the "Reset" or "Manage Product > Reset Product Activation" link.
Confirm: Verify the details and click "Yes". Your code is now "free" and ready for a new installation. 2. Generate a New Challenge Code
Each offline activation requires a unique Challenge Code generated from the new host machine.
On your offline scanner, open a command prompt or terminal and run:
Windows: C:\Program Files\Tenable\Nessus\nessuscli.exe fetch --challenge Linux: /opt/nessus/sbin/nessuscli fetch --challenge
Copy this alphanumeric string; you’ll need it for the next step. 3. Obtain the Offline License File
With your Activation Code reset and your new Challenge Code in hand:
Go to the Nessus Offline Registration page on an internet-connected system. Enter your Challenge Code and your Activation Code. Click Submit.
Download the nessus.license file and the compressed plugin file (the Custom URL provided is key for future plugin updates). 4. Complete the Registration
Move the nessus.license file to your offline scanner and register it using the command line:nessuscli fetch --register-offline nessus.license Quick Tips for Offline Management
Permissions: Only the Primary Contact or Product Owner can reset activation codes in the Tenable Community.
Plugin Updates: Because you're offline, you must manually download plugins using the unique URL provided during registration and install them via nessuscli update .
Avoid "Floating": While you can transfer licenses, Tenable scanners may eventually "time out" or complain if they don't receive plugin updates for 10–15 days. nessus offline activation license already in use
By following these steps, you can bypass the "License in Use" hurdle and maintain your security posture in even the most restricted environments.
When attempting a Tenable Nessus offline activation, the error "license already in use" typically indicates that your activation code is still linked to a previous installation or a different hardware ID. Because Nessus licenses are locked to a single host, you must manually release the code before it can be applied to a new offline environment. Why This Error Occurs
Nessus ties your activation code to a specific Challenge Code generated by your machine. If you previously registered the code—even on the same machine before a reinstall—the Tenable registration server sees it as "in use" and prevents a new license file from being generated. Step 1: Reset the Activation Code
The most effective way to clear this error is through the Tenable Community portal.
Log In: Sign in to the Tenable Community Support Portal using your administrator credentials.
Navigate to Products: Select My Products from the upper right corner.
Manage Product: Find your Nessus Professional license and click Manage Product.
Reset Activation: Click the Reset Product Activation link. Confirm the action when prompted. This "unlinks" the code from any previous host, making it available for a fresh offline registration. Step 2: Generate a New Challenge Code
Once the code is reset, return to your offline machine to generate a new challenge string. Linux: Run /opt/nessus/sbin/nessuscli fetch --challenge.
Windows: Run C:\Program Files\Tenable\Nessus\nessuscli.exe fetch --challenge in an elevated command prompt.
macOS: Run /Library/Nessus/run/sbin/nessuscli fetch --challenge. Step 3: Complete Offline Registration
With the reset activation code and the new challenge code, you can now generate the nessus.license file.
Visit the Tenable Offline Registration Page on a machine with internet access. Enter your Challenge Code and Activation Code.
Download the nessus.license file and the plugin archive (all-2.0.tar.gz).
Transfer these to your offline machine and register the license using: Command: nessuscli fetch --register-offline nessus.license. Additional Troubleshooting
Full Reset: If the software itself is stuck in a weird state, you can use the nessuscli fix --reset command to wipe existing registration settings on the local host before trying again.
Plugin Delays: After successful activation, it may take roughly 10 minutes for the Plugin Set to populate in the web interface.
To resolve the "license already in use" error during a Nessus offline activation, you must reset the activation code through the Tenable Community portal before it can be applied to a new challenge code 1. Reset the Activation Code
Since a Nessus license is tied to a specific host's hardware (via a challenge code), you must release it from the old host first. to your account on the Tenable Community portal Navigate to My Products in the upper right corner. Select your Nessus Professional product and click Manage Product Reset Product Activation
link. This unlinks the code from the previous machine and makes it available for a new registration. 2. Generate a New Challenge Code
On your offline machine, you need a fresh challenge code to link with your reset activation code. /opt/nessus/sbin/nessuscli fetch --challenge
C:\Program Files\Tenable\Nessus\nessuscli.exe fetch --challenge /Library/Nessus/run/sbin/nessuscli fetch --challenge 3. Complete Offline Registration Once you have a new
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
file and the plugin archive provided on the confirmation page.
Transfer these files to your offline machine and register the license using: nessuscli fetch --register-offline
for the Tenable account has the permissions required to reset an activation code. E-SPIN Group once the license is active? Update License Offline (Tenable Nessus 10.11)
When performing an offline activation for Tenable Nessus, encountering the error "Activation Code already in use" occurs because Nessus licenses are locked to a single host's hardware signature at a time. To resolve this, you must manually reset the license in the Tenable portal before it can be used on a new (or reinstalled) offline machine. 1. Reset Your Activation Code
Before you can generate a new offline license file, the existing "link" to your previous installation must be broken. Log in to the Tenable Community portal. Navigate to My Products (usually in the upper right). Select your Nessus product type and click Manage Product.
Locate the specific activation code and click the Reset or X icon.
Note: Only the primary contact or product owner can perform this reset.
There is a limit on how frequently you can reset the code this way; if blocked, you must contact Tenable Support. 2. Generate a New Challenge Code
On your offline machine, you need a new challenge code that reflects the current hardware. Linux: # /opt/nessus/sbin/nessuscli fetch --challenge
Windows: C:\Program Files\Tenable\Nessus\nessuscli.exe fetch --challenge
macOS: # /Library/Nessus/run/sbin/nessuscli fetch --challenge 3. Obtain the New Offline License
Once you have the challenge code and a "clean" activation code, you can generate the license file on an internet-connected machine. Go to the Nessus Offline Registration page. Enter your Challenge Code and Activation Code. Click Submit.
The page will provide a link to download a nessus.license file and a link for the plugin compressed archive. 4. Register the License on the Offline Machine
Transfer the nessus.license file to your offline system and register it via the command line.
Linux/macOS:# /opt/nessus/sbin/nessuscli fetch --register-offline /path/to/nessus.license
Windows:C:\Program Files\Tenable\Nessus\nessuscli.exe fetch --register-offline C:\path\to\nessus.license Common Troubleshooting
Deactivate Old Hosts: If the old machine is still accessible, you can try to "unlink" it locally by running nessuscli fetch --deactivate while it has an internet connection, though this is rarely possible in air-gapped environments.
Reset All: If the local installation is corrupted, you can perform a full reset of the local scanner settings using nessuscli fix --reset-all before attempting the new offline registration. Update License Offline (Tenable Nessus 10.11)
Troubleshooting the "Nessus Offline Activation License Already in Use" error can be frustrating, especially when you are working in a secure, air-gapped environment. This specific error typically triggers when the Nessus activation code is already linked to a specific Challenge Code or Host ID in the Tenable system.
Because offline licenses are manually tied to a unique hardware fingerprint, any change in your system configuration or a previous failed installation can block a new activation attempt.
Here is a comprehensive guide on why this happens and how to fix it. Why You See the "License Already in Use" Error Logs and data (typical Linux install):
When you perform an offline activation, you generate a "Challenge Code" from your local Nessus scanner. You then provide this code and your "Activation Code" to the Tenable website to receive a license file (nessus.license).
The error occurs because Tenable's license server believes the code is currently active on another machine. Common causes include:
Reinstallations: You uninstalled Nessus and tried to reinstall it on the same machine, but the server didn't "release" the old hardware ID.
Hardware Changes: If you changed the network interface card (NIC), CPU, or hostname, the Challenge Code changes, making Tenable think it's a new device.
Virtual Machine Shifts: Moving a Nessus VM to a new host often changes the hardware UUID, triggering a license mismatch. Step 1: Reset the Activation Code
The most direct way to resolve this is to reset your license through the Tenable Support Portal or the Tenable Community site. Log in to your Tenable Portals account. Navigate to the Products or Licenses section.
Locate the Nessus activation code that is giving you trouble. Look for a "Reset" or "Unlink" button next to the license.
Confirm the reset. This frees the code to be paired with a new Challenge Code.
💡 Note: Tenable limits how many times you can reset a code manually (usually once every 24 hours). If you have exceeded this limit, you must contact Tenable Support to request a manual reset. Step 2: Generate a New Challenge Code
Once the license is reset on the Tenable side, you need to get a fresh Challenge Code from your offline scanner to ensure you aren't using cached, stale data.
For Linux:Open your terminal and run:/opt/nessus/sbin/nessuscli fetch --challenge
For Windows:Open an Administrator Command Prompt and run:C:\Program Files\Tenable\Nessus\nessuscli.exe fetch --challenge Keep this new string of characters handy for the next step. Step 3: Perform the Offline Activation Again
With a reset license and a new Challenge Code, you can now generate the license file. Go to the Tenable Offline Activation page. Enter your Activation Code (the one you just reset). Paste your New Challenge Code. Click Submit and download the nessus.license file. Copy this file to your offline machine. Step 4: Apply the License and Plugins
On your offline scanner, apply the license using the command line:
Linux:/opt/nessus/sbin/nessuscli fetch --register-offline nessus.license
Windows:nessuscli.exe fetch --register-offline nessus.license
After the license is accepted, remember that you will also need to manually download and install the latest plugin set (all-2.0.tar.gz) since the machine has no internet access to pull them automatically. Pro-Tips for Avoiding Future License Issues
Unregister Before Moving: If you know you are going to decommission a server or move a VM, run nessuscli fix --reset first to try and release the binding.
Static MAC Addresses: If running Nessus in a VM, set a static MAC address. If the MAC address changes, the Challenge Code changes, and your license will break.
Documentation: Keep a record of which Challenge Code is paired with which Activation Code, especially if you manage multiple offline scanners.
If you followed these steps and still receive the "Already in Use" error, it usually indicates a backend sync issue at Tenable. In this case, providing your Activation Code and the new Challenge Code to a Tenable Support ticket is the fastest path to resolution.
