Adjust underfloor heating - defective?

Hello everyone,

we renovated the bathroom on the upper floor. The underfloor heating was working when we finished. However, it seems to have stopped working in the meantime. Unfortunately, I have no clue which settings I can adjust. Does anyone of you have an idea if everything is regulated correctly here? Apparently, the right connection is not working.

Maybe the actuator is defective. Maybe remove it and use it on/from another circuit.

I can't manage that on my own. Can I deduce anything from the pictures or the red marked fill levels? Otherwise, I don't see any difference between the individual outgoing distributors.

What happens if you press on that nose with the ribbing (on both sides) and then turn or pull it. The thing with the Zewotherm label has to be removed in the bathroom, then you can take a closer look.

Haha that's also my idea. I'm just afraid of doing it and damaging something. If you tell me that I can try it with a clear conscience, I will do it.

To me, it looks like someone screwed the sight glass from the bath in. That sits deeper than the others, doesn’t it?!