Here is some info on getting the mail merge to work with the attendee export file.
The below are two links that shows you how to turn the QR url to display the image and then how to re-size it as well on your badge face. Each is a little different. Some clients have had more luck with one over the other.
Youtube video: https://www.youtube.com/watch?v=-37BAGKzOv8
Attached is a .csv with some users and QR code links to test with.
**Note: If you have an integration please reach out to your client success manager for a more details on that process