I figured out the problem.
At the end of the day I had added Section Access to my app. I did not work in nPrinting after that until this morning.
I removed that and republished the app and now I can reload the metadata.
When will Section Access work with nPrinting? This is going to be a huge problem for us if it doesn't work. Or at least nPrinting can ignore it in the App. Blowing up is not an option.