TBMK- You only needed to change your email address in your original account.
By registering a "new account" you are seen (by Adobe) as a totally different client that cannot use the Serial Number associated with your 'old' account.
You will need to contact Adobe support for a chat.
! Contact Customer Care
Regards. My System: Lr-Classic 12.3 Photoshop 24.5, ACR 15.3.1, Lightroom 6.3.1, Lr-iOS 8.0.8, Bridge 13.0.3, Windows-11.