Sonoff TRVZB open window sensor not detected by better thermostat

Hi

I am configuring my valve with open thermostat, and it desnt seem to be able to detect the open window sensor.

The sensor exists, and is visible, as per the screenshot

But, when configuring this feature in BT, it doesnt seem to be able to reach it

What should i do to use that open window sensor with better thermostat?

Thanks