GnuCash-docs doesn't work

I have installed GnuCash 2.0.1 and GnuCash-docs 2.0.0 and all dependencies including enable_ofx without significant difficulty. GnuCash works well, and I am completing my transition from Quicken. My only problem is that I cannot access the GnuCash-docs. They are installed and active according to Port Authority, but nothing happens when I select either Tutorial and Concepts Guide or Contents under the Help menu. I'm sure there is something simple that I have overlooked. Any suggestions? Richard