Requested replacement unit from Google for broken Heatlink - to answer previous questions from CristianC:
How long has your thermostat been installed for? 18 months
Did the issue happen during the installation? No
Is there any error on the Nest thermostat display? No power
Have you had any power cuts recently? No
Have you had any work done on your electrical or heating systems recently? No
If yes, was the power properly restored at the fuse board after work was done?
How many zones ( thermostats ) are present in the setup? One
