Windows Server 2012 server with RD Web and RD gateway roles.
Remote Windows 7 client trying to login to a workstation via RD Web website
User can successfully login to the RD Web (Work Resources) website. However, secondary login to the actual Remote Desktop Gateway fails with error:
The logon attempt failed
The issue was cased by incorrect Default Web Site HTTP redirect on the Windows Server 2012 (IIS Manager).
Option "Only redirect requests to content in this directory (not subdirectories)" was not checked. After enabling this option, login errors went away.
Windows Server 2012