Where is the setting to enable/disable 2FA?

Where is the setting to enable/disable 2FA?

The following links show where enable/disable 2FA is supposed to appear, but neither appear for me:
  1. https://help.zoho.com/portal/en/kb/zohosites/faq/account/articles/how-do-i-enable-or-disable-two-factor-authentication-for-my-account shows Security > Two Factor Authorization, which does not appear when I visit that Security tab.
     
  2. https://help.zoho.com/portal/en/kb/accounts/multi-factor-authentication/articles/mfa-disable-multi-factor-authentication  shows a switch in the upper right corner, but there is no such switch when I visit that page.
     
  3. It's not even clear whether 2FA is actually part of MFA, or a separate feature.
So where is this setting?

Thanks. Graham