This is also the answer for the question “the machine installed with Nessus having hardware failure, need to relocate the license into different machine”.
Nessus activation codes can only be used by only one scanner at a time. If you need to re-install Nessus or get a ‘code in use’ error, then you will have to reset your code and register again.
To reset your code, from the Tenable Support Portal go to “Manage Nessus Activation Codes” and click on “Reset” for the code you want to reset. Note, you must be the ‘owner’ of the code (meaning the code is registered to your account) for the reset ‘x’ to show in your account. There is a time limitation on how frequently you can reset the Activation Code this way.
Once your code has been reset, you need to register your scanner. Please view the Nessus Installation and Configuration document for instruction on installing the Activation Code.