Nest thermostat

[Cars10]

My Nest thermostat does not trigger the boiler to fire on, even though the thermostat itself tells me that the heating is on.  No error codes. I currently have to manually start the heating on the Heat Link. How can I fix this?

[Frustratedddd]

Do you have a green light on the Heat Link normal mode, then pressing the button gives you 3 green lights?

Can you hear a click at the Heat Link when you turn the thermostat dial up, and a click when you turn the thermostat dial down?

Assuming the above is yes, then you could have a boiler issue. Obviously if the manual over ride is turning on the boiler, then you would assume the contacts are switching correctly in the Heat Link. The other way to test the relay in the heat Link, is with a simple neon screwdriver or tester.