As of 6/19/2017, Amazon has decided NOT to require 2-Step Verification to be implemented by all sellers on 6/30.
However, some seller accounts are still being prompted to set up 2-Step Verification.
Even though 2-Step Verification is not required, I still recommend setting it up for your own account protection.
Amazon has had a LOT of problems with seller accounts being hacked. In fact, hacking into active (or old) accounts is one way the “Just Listed” sellers have been using accounts with good feedback to hijack listings.
So, if you have not yet set up Two-Step Verification, I highly recommend that you do it now.
Two Step Verification Set-Up Tutorial
This two-step Verification Tutorial is structured using an Authenticator App as the primary verification method. Amazon does offer the option to use your cell-phone as the primary authentication method.
If you choose to do that, the process is the same, but the cell phone and Authenticator App steps are reversed. Amazon walks you through this during setup.
The RED numbers on the images below, walk you through the process step-by-step.