Please help before I have to return all the kit?

Hi, brand new setup here. Got the tado smart wired thermostat connected to a valiant eco tech pro 28 (Older model)
It’s currently replacing the wired thermostat from valiant and just using the ebus + and - wires.
My problem is when I set the device to d07 which I believe is required to operate my boiler the unit basically stops being a zone controller.
Anyone have any ideas why this would be happening? I’ve rebooted, reinstalled and re-pared it. Still happens every time

If anyone has any ideas that would be most appreciated.