Have you done a trial of any Adobe Apps with the Abobe Creative Cloud Desktop App ? Or installed this App? (This would convert your Lr6 to a subscription version and a "trial".)
Activation (& Deactivation) issues can only be handled by Adobe staff.
Activation or Deactivation versions of Lightroom
Lightroom 6 End of Support
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.