Prevention and operational best practices
you must "unlink" the code from the previous installation before the offline registration page will generate a new license for your current challenge code Immediate Fix: Resetting the Activation Code nessus offline activation license already in use
: On the offline Nessus host, run the following command to get your unique challenge string: Linux : /opt/nessus/sbin/nessuscli fetch --challenge Prevention and operational best practices you must "unlink"