I have one Collection in which when I try to find faces, Lightroom says "no faces". This is for a Collection with *lots* of faces. (This is in the latest version of Lightroom CC.)
With other Collections, I don't have this problem. The only way I can identify people is to go through one at a time and put the boxes around faces of those I recognize and put in their names. How do I get Lightroom to work correctly (as it had earlier today) in finding faces through the Collection and letting me deal with them as normal?
I've Googled this question and only found one person saying that if something like this happens to Select All the photos, rotate them, then rotate back and that somehow will reset Face Detection. But I tried that and it didn't work for me.