UPDATE: solved. I have a full gray beard which includes a huge moustache that covers my mouth. The camera could not find my mouth and jawline, I'm guessing. When I had someone else sit in front of the camera, the markers appeared fine. When I open my mouth and contort my head a little, the markers show up, sort of. I say 'solved', but now I know I can't easily use this feature as long as I have my beard.
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I too have the exact same problem. Using a Logitech webcam C930e USB camera. The camera connects, including to the Face3D server, green dots on servers, my face is shown, but no markers, and yes, the box is checked. CTA 4.3 Pipeline Paid.
What were the answers to the other inquiries about this?