Blurb upload (cannot log in from Lightroom)

Although I know I am using the right username and password, I cannot successfully upload my book to Blurb from the Lightroom Book Module. It keeps saying that my username or password is incorrect. 

(I don't have a problem logging in directly to Blurb from their own website, though). I have uploaded several books in the past, so I am not sure why it is an issue this time.

Any thoughts?