Start from the top in the upper register. Whenever you come to a hole that doesn't work, put a piece of plastic wrap (Saran Wrap, Gladwrap, whatever) over the hole and close the key to seal it. If it now plays then you have a leak. Fix the leak and continue working your way downwards. Good luck.
Update. Working on leaks but probably backtracking. Family health issues have halted the project on and off and other problems have been cropping up.
Lucky me! I broke an ear off a screw rod. Now I get to buy another die, but luckily I found one that may be a better fit than the one I broke. There are a few others that could probably use replacing too. I'm finding the set screws holding the posts are not doing a great job and have to remove and add glue under a few posts. I'm getting used to feeler gauge detection of leaks.