Using RWWGuard installed on an SBS server does not redirect all sites to the proper 2FA logon prompt.
There is an IIS module missing that performs the RWWGuard site redirection.
This issue is resolved using the most recent releases of RWWGuard. To fix this issue uninstall the existing RWWGuard client and install the most recent client from http://www.scorpionsoft.com/downloads/2fa
Or select the appropriate version below.
SBS2008 & SBS2011 using RWWGuard.