A few years ago, like many on here, I was a Lightroom user and I had both Canon and Nikon cameras and briefly flirted with the idea that converting all my raw files to dng would be a way of having a universal starting point for my processing. Shortly afterwards I sold my Nikon kit and now exclusively Canon and all my files from that time forward are standard CR2.
I do have quite a few dng files in my archive. PL recognises some of these and they can be processed as any raw file but others don’t even appear in the browser. So much for being a universal starting point.
Would have been good to have a go at reprocessing some of my older images but sadly it doesn’t appear to be possible in PL though these files can be browsed in other software without issue.
All the dng files I have checked show Adobe Lightroom as being the creating software and all taken with a Canon 600D so source files were .CR2 but I have lost / deleted them.
So same software same camera, some are processable in PL and some aren’t. Strange …
Could you, please, provide us with some DNG unsupported files for the analysis? You can upload them here under your name (instead of the ticket number) upload.dxo.com and let me know when ready.