I believe it should update automatically every time there is a temperature change. When you joined it to Hubitat, did it automatically pick the "Generic zigbee thermostat" driver, or did it join as a "Device", and then you selected that driver?
In either case, you might want to hit the Configure button on the device page a couple times.
Should there be no other resolution, setup a simple RM to do a device refresh every n minutes. One minute may be a bit too often causing hub overhead, I use 5 minutes.
That's basically what I ended up doing, though I stuck with the 1 minute updates. I'm not doing a lot with my Hubitat at this point so it's not that busy.
I've got the Rule Machine rule refreshing the thermostat every 2 minutes, but it still doesn't like to do it. Yet I can still go to the device page and hit Refresh and it responds.
Is there something different about the way a Rule Machine refresh works vs sending the refresh command from the device page?