Problem with Blurb results - undersaturation

I have printed two excellent travel photography books in the past with Blurb.  I have also used Shutterfly and Costco with great results.  However, I just completed my third Blurb book and made the mistake of ordering two initially only to be very disappointed when they arrived.  Both (one soft cover, one hard) show noticeable desaturation in all the photos.  The books look flat/dead.  Response from Blurb has taken a while, but they are not offering to replace the books, rather saying that the printing is "within tolerances."  It clearly isn't, to my eye.  (Yes, I use a calibrated monitor.)  Is there some setting in Lightroom Classic which affects the color space of the photos being uploaded to Blurb?  I cannot find it if there is, and the book module helps are, shall we say, "light."  (Lite!)  Is there something I could be doing incorrectly?  With 5-6 previously published books that have had no problems I don't see how, but am open to suggestions. 

Duane