Thank you @Karen I think I have lost my shutterfly marbles! If I only do a book or two a year, I forget their system and of course they do like to play around with their methods! Now I have a base for my next book or two this week. Fingers crossed!
I did download their template for the cover when I did my book, I had to expand the background quite a bit to fit the cover space. I was getting a similar error when I added my "page" to the cover, so went in search of the cover template.