Child can't see YouTube even when I allow it

We have 360 Premier Edition, installed on a PC that runs Windows 7 and uses Mozilla Firefox as a browser.  When I check for updates for Norton, it says we have the most up-to-date version.

I entered youtube.com into the "specific websites to allow" field for my son on Norton Family's House Rules section for my son. But my son was still unable to visit YouTube.

So I then selected "Give a warning but allow (my son) on the site anyway" in the 'How do you want to supervise Web activity?' section. But my son was still unable to visit YouTube.

So I then turned off Web Supervision for my son altogether.  But my son is still unable to visit YouTube.

Any suggestion for this problem? Thanks.