Heating control by using PID controller

Platform Information:
Hardware: Raspberry Pi 4
Operating system: openhabian
openHAB Version: openHAB 3.2.0 - Release Build
Temperature sensors: Shelly H&T
Actuator: Möhlenhoff Alpha 5, controlled with Shelly 2.5

Problem of the topic:
In my house with underfloor heating, I would like to be able to monitor and adjust the temperature of each room individually using Main UI. For this purpose I would like to use a PID controller.

Since the PID controller rule integrated in OpenHAB is still relatively new, I haven’t found any beginner-friendly examples yet. I have tried to fill everything in as good as possible, but am failing and I don’t know why. I hope someone can put me on the right track.

The actuator is normally closed.so if the PID Controller triggers, the command ON should be sent to the Shelly and the valve should open.
But no matter what setpoint I enter, the actuator is always open.

Any ideas, hints, help or further ideas on how I could program the underfloor heating are greatly appreciated.