If the files are in the same place, then it means the paths in your project might have been changed. Firstly, make sure the files are accessible, and by this I mean to open them to see if they work. Secondly, open the Picasso Album maker and check the paths of the images added to your book. Right click an image and verify the path.
Thirdly, export the book as it is to a temporary format and launch it. This might be a problem with the thumbnails while the original files will show after you compile or save the book.
