In the image source folder, Face Crop will create a file called CropData.txt. It is a comma delimited text file. Open that up in a spreadsheet. Make sure to choose comma delimited so it will parse the data correctly into the cells. There will be a column for errors. That will tell you which files have errors and what the error is. That will make it easy to know which files didn’t get cropped.
What error does it say in the column?