Yeah it's a two of two port s plan. The valve works. It's something between the heatlink and boiler. It's not switching the boiler on, only swithcing the valve. CH works fine.
I have recently installed the Nest v3 on a new set up. Ideal System 24 (with OT) and a Tribune XE water tank. Central heating is working, but we can't get the call for Hot Water to turn on the boiler - only flick the valve to allow water flow through the Tank - HELP!