Thermostat says E4: No power to the Rh wire, cannot turn on heating

[Shodan]

Hello, we have had a Nest thermostat running our heating system for over a year with no problems. Yesterday the nest thermostat ran out of battery power saying "H72: The thermostat isn't connected to the power supply". I charged up the thermostat battery using a USB cable but now it is saying E4: No power to the Rh wire.

Upstairs where the boiler is located, the Nest Link doesn't appear to have power. Pressing the central button does nothing and I have no means to control the boiler without Nest. We have no heating and we are self isolating due to Covid so we can't get an electrician to look at this for us. 

I've tried to get help from the installers and they say contact Nest. However the call me option isn't working at the moment, the call us doesn't show any numbers and live chat is not available.

Can the community help at all please?

Daniel

[Houptee]

You need to check if the transformer on the boiler that supplies 24-30v AC is good.  Do you own a multimeter? You set it to AC volts and pull the Nest off then put meter leads on R and C and see if you see 24-30 volts ac. If not go to the boiler and depending on the location of the transformer you can test for the voltage where the thermostat wires are connected and put meter on R and C at the boiler. Some boiler systems use a relay box where the t-stat wires connect and that is where the transformer is located. If no power then you need a new transformer. Post pics of the boiler connections if you can. 

[DukeNuke]

I have the same problem, and we have 24volts between the R and C wires. What should we do next?

[Houptee]

Take nest off and charge it with a phone charger see if it recharges. If it doesn't take a charge then possibly internal battery is bad. There is a way to replace the battery if you Google it but nest doesn't support doing it and you have to buy battery from ebay or other sites.