With a new thing and new device, a channel will show Null until it gets an update. Thermostat mode will usually only be updated seasonally. I’d suggest doing a “refresh” on the item and see if it populates.
if you are talking about Zwave items, the binding has changed very little in the last couple of years. Here I would try setting the binding to Debug and using the Zwave viewer to see if there are clues. Also there was a post about zwave debugging here.
Bob