On
MDE I go to
"Annual Passholders" under "My Account" in the dropdown. This page has a list of of info/links and there is a link under "Don’t Miss These Special Events and Passholder Extras" for "
View Passholder Extras". This takes you to a page that lists all the extras you can get, like the Flower & Garden magnets and discounts. There is one for early registration for runDisney and that takes you to the page I linked earlier.
Or I just Google "runDisney AP" because I'm lazy.
Edit: I just realized how I described how to get to that page is the same way you said wasn't working for you. Whoops!