Test by manually adding 'default.aspx' to the URL it should load the web page, like below: http://localhost/ra/default.aspx
If this works, then it means that the "Default Web Site" in IIS does not have 'default.aspx' listed as a "Default Document"
To correct this open IIS and go to the "Default Web Site", in the "Features View" double click "Default Document"
This will bring you to the screen below which will allow you to click "Add" on the right hand side of the screen.
Then just manually type in "default.aspx"
Test the URL to the NFA page again and you should now be directed to either the login page or directly to the NFA website depending on your SSO settings.
If the problem still occurs, it may be necessary to make the same change under "RA" as well as "Default Web Site".