Go to this folder: [Macintosh HD] / Library / Application Support / Adobe / Lightroom / Modules /
Right click the file “NegativeLabPro.lrplugin” and select “show package contents”
You should see a file named “NegativePresets.lua”. Is this file present? If it is all lower case, like “negativepresets.lua”, rename it to “NegativePresets.lua” with that exact use of upper case and lower case.