Help with my set up

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Hello all , I have been a tado user for years so I thought I would put it in the mother in laws home , connected bridge V2 and smart thermostat along with extension kit to replace her wireless thermostat , followed instructions and all I had to do was swap a cable from terminal 3 to 4 in the extension kit and use same back plate , hot water is fine from the combo boiler , the app reads the room temp and Alexa reads it fine , I have set it to lounge and to use the extension kit but trouble is when I raise temp on thermostat or via app the heating doesn’t come on , all day connected in app , the light in extension kit flashes on and off about very 2-3 seconds . When I press the manual override button the relays click and boiler fires up , am I missing something? Then tension kit and bridge are on latest firmware but the thermostat is still in firmware 24.1 so and old one , I can’t set it to blink or when I change temp via Alexa or app it you can’t see it adjust on the thermostat like mine does at home. Do I need to do anything in the installer menu on thermostat? Help appreciated please