I looked at you images. The faces in the silhouette images are too dark. If you can’t see the facial features in the image then neither can the AI face detection in most cases.
You can use Alignment mode 4 if you want it to align to the edges of the cutouts instead. That will snap align to the top and bottom of the cutout and center based on the left-right edges. Mode 4 doesn’t use face detection so it will work with silhouette images. However, it can’t align the face to a location.
You could also use mode 4 along with the pause to scale option so it pauses for you to align and scale each image. Given the variety of poses, you probably would want to align each one anyway since all of the poses are different.