I have done all my conversions on a Windows laptop, and then copied the files to my Mac. The NEF and xmp.
Now the NLP settings are not there anymore. Mening when I open the NLP dialog box its seems like a new file, I need to convert again.
On both computer the versions are the same.
The original files are NEF, with a xmp sidecar.
A similar topic has been addressed in here: Moving NLP-edited files between computers
Hope it helps.