Issue Importing DNG Files into Photos App

I can import RAW photos in .ARW format no problem, but in Adobe Lightroom when I create an HDR image it exports it as a .dng.

When I import the .dng file into photos this file does not show up as an image in my Photos library (it's essentially a blank white rectangle), and when I try to open it it opens without showing the image. When trying to edit within photos, it says, "photos cannot edit this image because it uses an unsupported format". -- any suggestions on how to get these raw .DNG photos into the photos library so it will sync in RAW to iCloud?