This isn't exactly a connection issue as the app and Nest thermostat connect perfectly well. The problem is that the app (on both android and IOS phones) only allows us to control the hot water not the heating. The hot water circle lights up, we can boost etc, but the heating circle is just black. The dial is stuck on a room temperature of 23 - the actual temperature and the temperature on the thermostat is currently 17 - cold!) You can toggle the arrows on the circle, but even if you toggle up beyond the 23, the heating does not come on. Google Nest have been absolutely useless - have tried help for both the app and the thermostat and have achieved nothing. Can anybody out there help?