I have two sites with Google Authenticator plugin.
On one of these websites, today I noticed, the authenticator box on the login page didn't appear anymore.
To test what this was caused by I updated plugins on my other website. (I updated iThemes Security and WordPress SEO... my guess is that iThemes security caused the problem).
After updating these plugins the authenticator box also is gone on the login page of the second website.
I updated iThemes Security from version 4.0.5 to 4.0.14, with 4.0.5 there was no problem.
Your help would be appreciated.