PDF Thumbnails Not Displaying in Drupal 2.6.1

We are running:
Windows Server 2008 R2 Standard
Version 2.6.1 of Omeka
xampp-win32-5.6.32-0-VC11-installer
ImageMagick 6.7.5 Q16
Ghostscript 9.26
I didn’t fix the problem and I rolled back the change. How can I make the pdf thumbnails display?

Thank you for your help