3rd gen not calling for heat

[Kayteemac]

Hello! Yesterday my 3rd gen thermostat stopped calling for heat. My furnace cycle starts but the burner doesn’t ignite. I had a technician come out and he jumped the thermostat to make sure that was the issue. I tried charging it through usb but after 5hours the green light was still blinking - I reconnected it and it has 3.7V but still reads that my temp is 20° even though it was only 11° in my frigid house. I cranked it up to 30° but it still wouldn’t allow my furnace to kick in. I have had no error codes or messages sent to my app. Wifi is properly connected.

any ideas?

thanks in advance

[Kayteemac]

In addition: I left the thermostat plugged in overnight and the green light is still flashing. 

[MarkSweeney]

I have a very similar story in that my Nest has been working perfectly for around a year, and all of a sudden it has stopped communicating with my heating system. All seems well on the thermostat, showing heating in progress, but it’s not actually opening the motorised valves which in turn would activate the pump to circulate the hot water  in my  central heating circuit, or hot tank. The light on my heat link is green and seems to be communicating with the thermostat as usual. The heat link makes a click sound when you activate the system manually by pressing the big centre button, however it doesn’t control the motorised valves as it should. I’ve tried a reset on both heat link and thermostat with no joy. My heating system is working perfectly when I manually switch my motorised valves to the open position. It’s so weird and driving me nuts. It just happened a few days ago after working perfectly sine the install. I wonder if there has been some kind of update recently?  Nothing has been changed with my system or anything, it just stopped working a few days ago like your issue and not actually controlling the signal to call for heat. Strange