I installed two of these last weekend and I had similar issues. I worked on it for hours, tried the other lock and it went through fine. Turns out, one of the locks I had didn’t have the right guts in it, the instructions didn’t match the product and I had to exchange it.
When I worked on the one that DID have the right guts, I was having issues connecting. What I realized is the model names and descriptions of the lock don’t match up with the app. When I tried to add the lock manually in ST, I selected the device that had ZP in the model name for the Zwave Plus. I think the description is wonky or something there is why I kept selecting the wrong one at first. When you select the z wave plus device, it allows you to just scan the qr code and presto it connected perfectly for me.
As I typed this, I went to get a screenshot of the one I selected and it looks like the device descriptions have changed slightly because now NONE of them mention model numbers but I’m certain this was the one I selected:
They must’ve seen me trying to connect a bazillion times in the logs lol.
It may not be the same issue but this was the trouble I had a few days ago and how I fixed it. Ultimately I deleted the ST integration for the lock and integrated it through Ring alarm because it had more bells and whistles with the locks.