When you copy the nap_update.plf file to the USB stick on a Mac, it also creates a .nap_update.plf file used for tracking information about the file. There are also a number of other files created by the Mac that are hidden on the Mac but not on a Windows computer or the skycontroller. The .nap_update.plf file shows up first in a directory listing on a Windows computer . The skycontroller also sees the .nap_update.plf file first before the nap_update.plf file, and tries to use the first plf file it finds. If you put the USB stick in a Windows computer and delete all other files and folders then it will work. I created an action script so I can right click the USB stick then select my action script to remove all the files and folders starting with a period from the USB stick. Update works properly after that.