When I follow al the steps to configure Zwave JS UI, the I put in the ws-URL: a0d7b954_zwavejs2mqt:3000. It cant connect… 
In the Zwave JS UI it shows my devices
The URL is ws://a0d7b954-zwavejs2mqtt:3000, all parts required.
I know, but does not work. “No connection”
Then it means the add-on is not running properly. Did you change any settings, like for the websocket server, that were not included in the installation instructions?
Not that I know of. I see under conficuration tab “Home Assistent” a WS Server option. Does it need to be on or off?
It should be on. All the settings are already configured for you, besides the serial path and security keys.
Yes it is on. Didn’t change anything else. Configured the keys, I see the devices in Zwave JS UI. But it still says “can’t connect” when I put the URL in.
Also reinstalled the add-on.
Now I don’t have the devices available in the dashboard. But I can see them in the Zwave JS UI…
Don’t know if I understand it.
But I have HA installed on a NUC
Do I need to open port 3000?
Yes the JS UI Addon in HA