Gutenberg PDF viewer not working

I have a PDF of storyboards on my server that is easily opened by Browsers and the WordPress plugins Wonder PDF, Real3D and PDF Embedder.
However, the Gutenberg PDF viewer block and the plugin PDF Light Viewer both give an error message of an unexpected server response (0) while retrieving the PDF.
I’m looking for a fix to allow me to use the Gutenberg PDF viewer, so I can see if it does a better job of displaying the PDF on mobile than the other plugins. (I’d rather not ask people to use a mobile app to open the PDF.)

The page I need help with: [log in to see the link]