Ha, I think I found the problem. Rev 2.3 of the Waveshare HAT adds a PWR pin. It seems that pin must be set HIGH to turn on the display: https://github.com/waveshareteam/e-Paper/commit/6ec0aacc4347d1efd7f7aad778f48591de751049

I tried setting that pin high in node-it8951 and I finally got a response from the display when MM started up! I just need to add a delay to give the display time to start up. So progress!!