There seems to be an issue with adding WL books today.  There's a delay from the time you add til the time it shows up on your WL that I've never experienced before. The search function shows I added both the PB and HC editions of a book yet to be published this year. The PB has now shown up on my WL, but not the HC even though when I click on "expand" your WL, it shows that I have already added the HC version.

There shouldn't be any delay. It may be a problem with how you have the WL sorted. It may be showing up somewhere you don't expect it too or not at all if sorted by a field that is left blank on the HC edition.

eta: Resorting by Date, descending works the best to find problems in this type of thing. When I do this to your WL I see that the James Patterson HC's title is entered incorrectly so it will show up in a different place on your WL. Is that the book you are talking about? It is on your WL, it just won't be listed by the paperback if you sort by title.

It's possible that your browser is showing you a cached image of your wish list page rather than the updated page.  To do a hard refresh, hold down the CTRL button and hit the F5 key.