You may have to enable in your firewall settings.

Once, back in the day I was using AVG's free firewall, I changed some setting and had to enable Microsoft Help manually in the configuration.

I no longer use AVG, but in OneCare, the first time I needed to use Outlook help, 'Microsoft Office Help Viewer' had to be allowed first.

Which firewall are you using and have you made any changes to it of late?

@goodguy. It would have been more helpful to us, If you had said that in your original post. Us geeks tend to know specific things. And changing things as you go along, does not help.