There are a couple of reasons of why pictures may not have been synced from the online family site to Family Tree Builder:
1) You have more than one tree on your family site and you have uploaded photos directly to your family site without tagging them.
In Family Tree Builder 7.0, we do not currently sync the project photos when you have more than one tree on the family site. Personal photos for people in the trees will be synced regardless of whether you have more than one family tree on the site or not. Any other photos that were added on the site will not sync back to your project in Family Tree Builder.
2) It is possible that you previously deleted a photo from your project in Family Tree Builder:
When you delete a photo in Family Tree Builder 7.0, it will no longer show in the software, however, the photo will still be located on the online family site. This means that you may find some photos that appear in the online family tree but not in the Family Tree Builder.
In order to restore the photo, you will need to manually add it by doing the following:
Find the picture in the family site:
Click on the photo to view it in full size, and click ‘Download’ to save it on your computer:
Delete the photo from the family site (so there would be no difficulties with duplicates) by clicking on the little ‘x’ button:
Add the picture to Family Tree Builder: How do I add photos to the Family Tree Builder?
Sync the project and you’re done.