I upgraded from version 8 to 11. I tagged many images with people tags. I had 4 people tags. After importing, the images still show the tags. However, under people view only two of the tags resulted in stacked photos. The other two tags report "no people exist in this group" if the tag group is selected. Why aren't the photos stacked for the people tags I prviously had tagged? How do I find all images with each of hte tags?