For those having trouble with the new SmartThings app and the NZW97, I think I stumbled upon a quick solution after trying way too many options (and discussing this on the SmartThings Community https://bit.ly/36oPPyW).
Anyway, problems started when I realized the other day that I could not control the NZW97 in the new SmartThings app. Pressing the on/off button on the device tiles didn’t work. The two child devices always showed “checking status.” After some experimentation, I figured out that if I go into the SmartThings IDE and first delete the two child devices and then change the DTH for the NZW97 to SmartThings “Inovelli 2-Channel Smart Plug MCD” everything works. You will wind up with one device tilte for the MC device but when you press it (not the on/off button), it will open up and all THREE channels will be displayed and you can press on/off in this display.
I thought there might be a problem because the two child devices were not being displayed in separate tiles, but if you want to add them to something like Smart Lighting, they are available for selection. So, all my automations continue to work as well.
Hope you find this helpful. Enjoy.