I left out a step in the post, sorry: you have to add 50books_poc to your network, in addition to tagging the link "for:50books_poc". (In the drop-down menus at the top, go to "People" and select "My Network." On the far right-hand-side of the page, near the top, there'll be a light blue box. The second item in that box should say "Add user to network.")

At the moment, the link hasn't come to the 50books_poc inbox yet. Do you want me to just add the link manually, or do you want to add 50books_poc to your network and see if that makes it work?