Adjust Facial Features not working in Photoshop Elements 15 on iMac

All of a sudden today I tried to Adjust Facial Features on my iMac and it keeps saying there aren't any faces in my photo.  There are two very prominent faces, so I am stumped.  I tried opening several versions of the same jpeg photo but it says the same thing on each one.  I've been on hold with tech support for about an hour so figured I'd try this instead.