I've created dng lightroom presets and have them for sale on my Etsy page. I've had a few customers tell me they're having trouble getting the presets to apply to their photos. Others, have had no issue whatsoever.
What could be the problem?
Download and install, How to, Performance, Presets or profiles, Problem or error
I did ask them for details, and that is what they provided me with - they are unable to get the preset to apply to the photo. When the preset is selected, it does not change anything on the photo, it doesn't apply.
You need to ask the user what OS and LrC version, file type ( raw, JPEG, etc.), and camera model they are using, and the specific preset that isn't applying. Then upload that specific preset to Dropbox or other file sharing site and we can take a look at it.