1. After you process the photos do you receive any error messages?
2. What image format do your photos have?
3. What operating system do you have (e.g. Window 10 / macOS Sierra)?
Here is a step-by-step video tutorial for date stamping photos in bulk:
You can try a test run with the sample photos from Windows/Mac and see how this goes.
Please let me know if this solves your problem.