FWIW, I had exactly the same symptoms with my Emporia Vue 2. It would connect to HomeAssistant and immediately disconnect.
I ultimately tracked it down to something silly. I was powering the Emporia Vue 2 with USB, since I had just flashed it and was trying to set it up before putting it in the electrical panel.
This meant that the two wires that the Vue 2 senses the mains voltage with weren’t connected, and as a result it was sending back “nan” as the voltage or similar to Home Assistant. Home Assistant was expecting a number, and so it was failing to parse and immediately disconnecting.
IIRC I discovered this by looking in HomeAssistant’s logs (e.g. http:///config/logs).
Hope this helps someone avoid wasting a bunch of time like I did!