/opt/nessus/sbin/nessuscli fetch --challenge If this returns nothing or an error, the instance is not activated. Try deactivating the current (old) instance if it still exists:
Would you like a template for contacting Tenable Support to expedite the license release? nessus license already in use
/opt/nessus/sbin/nessuscli fetch --deregister If successful, reactivate on the new instance: reactivate on the new instance: