When installing AuthAnvil Two-Factor Auth on Server 2012 the AA Manager https://FQDN/AuthAnvil/Manager/Logon.aspx page will not correctly render in a browser, the images are missing.
There is a missing Web Server Role that needs to be installed.
If you enable Static Contect in the Web Server Role the issue will resolve.
Web Server > Common HTTP Features > Static Content
All versions of AuthAnvil Two-Factor Auth installed on Server 2012 unless otherwise noted.