Facebook Page Managers

Facebook will be requiring users who manage Facebook pages with a “large” reach to implement two-factor authentication as part of its increased security aka “transparency” initiative. In addition users will need to confirm their primary country.

This will start first in the USA before rolling out globally. Facebook doesn’t actually explain how ‘large’ a Page needs to be in order to qualify, but if you find that you do require authorization, you’ll see a notice at the top of your News Feed to begin the process.
If you do not complete authorization by the deadline provided in their notification, you will lose the ability to post as the Page.