/opt/nessus/sbin/nessuscli fetch --register <online-activation-code> If you have a now, you cannot directly convert it — you need a standard online activation code from your Tenable account. 4. If registration fails because it’s already offline‑registered First reset the registration:
Here’s the standard process: Run this command on the Nessus host: nessus offline mode to online mode
To switch Nessus from to Online Mode , you generally need to re‑register the scanner with a valid activation code while connected to the internet. Offline mode is typically used for air‑gapped networks where the scanner cannot reach Tenable’s cloud or license servers. /opt/nessus/sbin/nessuscli fetch --register <