I'm glad to have found this older thread, I can't get my Shelly Motion to work either. It's somewhat comforting that it's not just me. I've probably spent five hours on it. I do fine up until the point where I open the Shelly App. The Discovered Devices opens for about 1/2 second, then disappears. I have tried using my WiFi address, as well as inputting the devices IP address.
I don't use Home Automation programs, rather I use Alexa for my mixed bag of stuff.
Has anyone found a solution? Is the solution to return my Motion and buy another brand? Help!