can you point us a a PID of a person with a photo in question so we can see as an example.
also note tha this option of clicking on the image only works for true image files (JPG etc.)
and does not work for PDF files.
also if it is a JPG image file and just doenst work - its probably an issue with the Browser/version you are using. try a different browser or even different computer - just as a test to see if that is the issue.
You click on the person you want to tag in the photo. A box appears and says Who Is In This Memory? Type the name. The system is slow so you'll have to wait. Suggestions may appear and you can pick your person, if not it will say Add New. If you Add New you'll have to go to the person's name in the left hand People box and add her PID number.