Next 3gen Smart Thermostat and Heatlink OK, but no heating

[KGJ58]

Hi,

My 3g thermostat and heatlink have been working for over two years with no problem.  Recently, they have stopped controlling the radiator and water heating.  Both seem to be operating fine, thermostat is working, connected to wifi, lights on the Heatlink are OK, but heating won't turn on.  Am I missing something simple here?

[Frustratedddd]

Just to confirm, are you saying there is a light on the Heat Link?

What happens if you press the button on the Heat Link, does the boiler fire up?

Do you have motorised valves?

[KGJ58]

Yes, when I press the button the lights come on.  However the boiler doesn't fire up.

[Frustratedddd]

Do you have motorised valves?

Do you have a Neon or mulimeter or any type of tester? Would you be able to test the connection if you do?