One of my favorite authors has a new book that is not "known" to PBS.   It there a way to get it added, so I can put it on my WL?

Just keep checking - PBS is good about keeping updated.  Make sure you have the correct information/spelling.  And if possible, if you have the ISBN number, you can search by that also.

On the page that tells you the book wasn't located, did you click on the blue link that says "don't see what you're looking for" (or something similar to that), off to the right, close to the top.  Try that.

Betsy;  search Amazon or B&N for the ISBN# for the book you want. Then put the number  in Advanced Search and click "wish listed books" on the bottom. The book should come up and then click to add to your WL.

ETA: you can also put the ISBN# in Google search.

I would search the author's website, Amazon, Barnes & Noble to find the ISBN.  Title doesn't always work as they can be changed right before the book is published. I was looking for a sequel to a book I read, there was even a sample chapter in the 1st book.  I finally found it-they had changed the title between the time the 1st book came out and the 2nd. 

Also check to make sure when you're searching that you're also searching unposted books.  Sometimes I forget and think "wow, they don't have a listing for that?" but it's only showing available books.