How to Log in to Twitch with One-Click
The ability to create a new Twitch account linked to your Facebook account or to link your Facebook account to your Twitch account has been removed from the Connections portion of Twitch User Settings for existing Twitch accounts.
Twitch plans on removing the ability to login with linked Facebook account on April 2nd, 2020.
It is highly recommended that you make sure the email address associated with your Twitch account is up to date before April 2nd, 2020. For more information about how to update your Twitch email address, please click here.
If you have an account that was already linked with Facebook, then you can continue to log-in to Twitch with One Click but only until April 2nd, 2020.