Safari Bookmark icons/blue dots

Re: Safari 10.1 running on Sierra 10.12.4. I've noticed recently that when looking at my bookmarks in the favorites bar at the top of the Safari window, the bookmarks all just have blue dots now instead of the websites graphic icon. If I open a bookmark from the favorites drop down lists the icon will appear and stay until I restart the computer, after a restart all the bookmark icons revert to a blue dot again. This is mostly an aesthetic thing but I like seeing the icons. Any thoughts as to why they are not remaining after a shutdown/restart cycle.

Thank you for your assistance.