Hm, that wired. You could enable debug by following How to debug MQTT2 Binding issues? f.e.
Could you post the manufacturer and model name of the device?
Also the device should show up as supported and there should be a link behind the model like this:
Also the Output Setting is configurable via the webGUI:
Well, I created everything in openHAB via the Webinterface (I don’t like Textfiles anymore 
) so this should be fine.
Maybe try to give the device in z2m a friendly name which is shorter…