Hi Marco,
The addon problem is gone!
All I did was to finish all your OTHER steps, then enabled that addon, now it works. I don't know why.
One suggestion:
On the ABOUT page, the text is light grey color and it is very hard to read. Could you please help refine the css to give it a couple of more text style/color so that the ABOUT page is easier to read, and maybe provide us a template of ABOUT?
I know I am asking too much. But you are the expert with taste, so I better try to ask...