! 
I'm guessing that they were sold out at the end of 2021. The pre-registration link is dead and they were 2021 models and the 2022's are readily available.
Per the link you included:
1. Register
Sign up by filling out the registration form with details including your name, mobile number, email ID, state and city of current residence.
2. Generate Unique Code
The registration process will lead to the generation of a unique code. Keep your code handy which will act as your ticket for the online sale starting December 6, 2021, 7PM till stocks last.
3. Login @Sale Day
Login with your unique code during the online sale, starting December 6, 2021, 7PM till stocks last to participate and own a Royal Enfield 120th Year Anniversary Edition Continental GT or Interceptor 650.
2. Sale:
(a) Royal Enfield is inviting bookings for brand new 120 number of 120th year limited edition Royal Enfield Interceptor and Continental GT Motorcycles.
(b) In order to be eligible for participating in the Sale, Customer shall register himself/herself on www.royalenfield.com/in/en/120thedition/pre-registration/ during the registration period.
(c) Registration shall remain open from 12 P.M. IST on 24th November 2021 till 12 P.M. IST on 5th December 2021.
(d) Customer acknowledges that the colors/textures as they appear on the Website may vary from those on actual Motorcycles.
(e) Each Motorcycle will have a pre-fixed serial number that will be assigned to the customer based on the order in which the motorcycle has been booked on the Sale date.
Per the link you included:
1. Register
Sign up by filling out the registration form with details including your name, mobile number, email ID, state and city of current residence.
2. Generate Unique Code
The registration process will lead to the generation of a unique code. Keep your code handy which will act as your ticket for the online sale starting December 6, 2021, 7PM till stocks last.
3. Login @Sale Day
Login with your unique code during the online sale, starting December 6, 2021, 7PM till stocks last to participate and own a Royal Enfield 120th Year Anniversary Edition Continental GT or Interceptor 650.
2. Sale:
(a) Royal Enfield is inviting bookings for brand new 120 number of 120th year limited edition Royal Enfield Interceptor and Continental GT Motorcycles.
(b) In order to be eligible for participating in the Sale, Customer shall register himself/herself on www.royalenfield.com/in/en/120thedition/pre-registration/ during the registration period.
(c) Registration shall remain open from 12 P.M. IST on 24th November 2021 till 12 P.M. IST on 5th December 2021.
(d) Customer acknowledges that the colors/textures as they appear on the Website may vary from those on actual Motorcycles.
(e) Each Motorcycle will have a pre-fixed serial number that will be assigned to the customer based on the order in which the motorcycle has been booked on the Sale date.
