Ubisoft will lock R6 ranked play for players who did not activate two-step verification. The decision comes as part of Ubisoft's anti-cheat plans that have been announced earlier this year. 2SV will be mandatory only for PC players.
Ubisoft have announced that two-step verification will become mandatory for all Rainbow Six Siege PC players on 11 December 2018. To encourage players to activate the security feature, Ubisoft offers a free Thermite bundle which includes Ride or Die headgear, Compatriot uniform and Cyberfriend weapon skin for everyone who activates 2SV before it goes live.
Players who decide to skip the activation will be locked out from ranked play but access to Situations, Terrorist Hunt and casual play will still be there. Ubisoft is enforcing these security measures to reduce the number of cheaters which has been the studio's priority in 2018.
The ranked lock will apply to all regions except for East and South East Asia which will receive the lock at later date. Also, players on Steam will have to activate the authentication on their Ubisoft account. For now, the changes only affect PC players and there is no official information about implementation on consoles.
2-step verification will add another layer of security to Uplay accounts which will make them harder to hack. This also means that every purchase or password change on your account will have to be confirmed second time through your email or text message. Even if someone tries to hack your account everything will go through two-step authenticator making it almost impossible to break into your Uplay.
You can find detailed information on how to active two-step verification on Ubisoft's . We didn't really have the smoothest experience with the security feature since its introduction. It would often deactivate on its own and require re-activation but it was a while ago and hopefully, Ubisoft took care of these issues in the meantime.