Your Libronix Customer ID is typically the email address you were using when you first registered your software. It may be an old email address you no longer use.
Here's how to find it: open Libronix Digital Library System and click Help | About Libronix.
If you have never installed any Libronix Digital Library System software (Logos Bible Software Series X) but you do own a very old copy of the Logos 1.0 - 1.6 Bible Software, or a Logos Library System collection, please call 800-875-6467 and ask for end-user sales to find out what discounts you are eligible for.